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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Mar. 04, 2020	Jun. 28, 2019
Document and Entity Information
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Entity Registrant Name	Clean Energy Fuels Corp.
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		205,583,627
Entity Public Float			$ 535,652,621
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0001368265
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash, cash equivalents and current portion of restricted cash	$ 49,222	$ 30,624
Short-term investments	56,929	65,646
Accounts receivable, net of allowance for doubtful accounts of $1,919 and $2,412 as of December 31, 2018 and 2019, respectively	61,760	68,865
Other receivables	84,898	15,544
Inventory	29,874	34,975
Prepaid expenses and other current assets	11,109	8,444
Derivative assets, related party		1,508
Total current assets	293,792	225,606
Operating lease right-of-use assets	28,627
Land, property and equipment, net	323,912	350,568
Long-term portion of restricted cash	4,000	4,000
Notes receivable and other long-term assets, net	31,622	17,470
Long-term portion of derivative assets, related party	3,270	8,824
Investments in other entities	26,305	26,079
Goodwill	64,328	64,328
Intangible assets, net	1,229	2,207
Total assets	777,085	699,082
Current liabilities:
Current portion of debt	56,013	4,712
Current portion of finance lease obligations	615	693
Current portion of operating lease obligations	3,359
Accounts payable	27,376	19,024
Accrued liabilities	67,697	48,469
Deferred revenue	7,338	7,361
Derivative liabilities, related party	164
Total current liabilities	162,562	80,259
Long-term portion of debt	32,872	75,003
Long-term portion of finance lease obligations	2,715	3,776
Long-term portion of operating lease obligations	26,206
Other long-term liabilities	9,701	15,035
Total liabilities	234,056	174,073
Commitments and contingencies (Note 16)
Stockholders' equity:
Common stock, $0.0001 par value. 304,000,000 shares authorized; 203,599,892 shares and 204,723,055 shares issued and outstanding as of December 31, 2018 and 2019, respectively	20	20
Additional paid-in capital	1,203,186	1,198,769
Accumulated deficit	(668,232)	(688,653)
Accumulated other comprehensive loss	(1,566)	(2,138)
Total Clean Energy Fuels Corp. stockholders’ equity	533,408	507,998
Noncontrolling interest in subsidiary	9,621	17,011
Total stockholders’ equity	543,029	525,009
Total liabilities and stockholders’ equity	$ 777,085	$ 699,082

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 2,412	$ 1,919
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized (in shares)	1,000,000	1,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized (in shares)	304,000,000	304,000,000
Common stock, issued (in shares)	204,723,055	203,599,892
Common stock, outstanding (in shares)	204,723,055	203,599,892

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues [Abstract]
Total revenue	$ 344,065	$ 346,419	$ 341,599
Cost of sales (exclusive of depreciation and amortization shown separately below):
Inventory valuation provision			13,158
Change in fair value of derivative warrants	(1,039)	543	(46)
Selling, general and administrative	73,444	77,207	95,715
Depreciation and amortization	49,625	51,850	56,614
Asset impairments and other charges			67,934
Total operating expenses	334,137	342,524	476,046
Operating income (loss)	9,928	3,895	(134,447)
Interest expense	(7,574)	(15,924)	(17,751)
Interest income	2,437	2,857	1,497
Other income (expense), net	1,990	(566)	139
Loss from equity method investments	(119)	(2,723)	(131)
Gain from extinguishment of debt, net			3,195
Gain from sale of certain assets of subsidiary	7,455	4,782	70,658
Loss from formation of equity method investment		(1,163)	(6,465)
Income (loss) before income taxes	14,117	(8,842)	(83,305)
Income tax benefit (expense)	(858)	(341)	1,914
Net income (loss)	13,259	(9,183)	(81,391)
Loss attributable to noncontrolling interest	7,162	5,393	2,154
Net income (loss) attributable to Clean Energy Fuels Corp.	$ 20,421	$ (3,790)	$ (79,237)
Income (loss) per share:
Basic (in dollars per share)	$ 0.10	$ (0.02)	$ (0.53)
Diluted (in dollars per share)	$ 0.10	$ (0.02)	$ (0.53)
Weighted-average common shares outstanding:
Basic (in shares)	204,573,287	180,655,435	150,430,239
Diluted (in shares)	205,987,509	180,655,435	150,430,239
Product revenue
Revenues [Abstract]
Total revenue	$ 298,469	$ 307,839	$ 287,292
Cost of sales (exclusive of depreciation and amortization shown separately below):
Cost of sales	185,557	194,509	216,413
Service revenue
Revenues [Abstract]
Total revenue	45,596	38,580	54,307
Cost of sales (exclusive of depreciation and amortization shown separately below):
Cost of sales	$ 26,550	$ 18,415	$ 26,258

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income (loss)	$ 13,259	$ (9,183)	$ (81,391)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments net of $0 tax in 2017, 2018 and 2019	505	(1,305)	(113)
Unrealized gains on available-for-sale securities, net of $0 tax in 2017, 2018 and 2019	67	54	189
Release of foreign currency translation adjustments on contribution of subsidiary into equity method investment			16,712
Total other comprehensive income (loss)	572	(1,251)	16,788
Comprehensive income (loss)	13,831	(10,434)	(64,603)
Clean Energy Fuels Corp.
Net income (loss)	20,421	(3,790)	(79,237)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments net of $0 tax in 2017, 2018 and 2019	505	(1,305)	(113)
Unrealized gains on available-for-sale securities, net of $0 tax in 2017, 2018 and 2019	67	54	189
Release of foreign currency translation adjustments on contribution of subsidiary into equity method investment			16,712
Total other comprehensive income (loss)	572	(1,251)	16,788
Comprehensive income (loss)	20,993	(5,041)	(62,449)
Noncontrolling Interest in Subsidiary
Net income (loss)	(7,162)	(5,393)	(2,154)
Other comprehensive income (loss), net of tax:
Comprehensive income (loss)	$ (7,162)	$ (5,393)	$ (2,154)

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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+ Details

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (PARENTHETICAL) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustment, tax	$ 0	$ 0	$ 0
Unrealized gains on available-for sale securities, tax	$ 0	$ 0	$ 0

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest in Subsidiary	Total
Increase (Decrease) in Stockholders' Equity
Cumulative effect of adopting ASU (Note 1) \| Accounting Standards Update 2016-09 and 2016-16		$ 194	$ (497)			$ (303)
Adjusted Beginning balance	$ 15	1,090,555	(604,333)	$ (17,675)	$ 24,822	493,384
Adjusted Beginning balance (in shares)	145,538,063
Beginning balance (in shares) at Dec. 31, 2016	145,538,063
Beginning balance at Dec. 31, 2016	$ 15	1,090,361	(603,836)	(17,675)	24,822	493,687
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of offering costs (in shares)	6,112,906
Issuance of common stock, net of offering costs		12,454				12,454
Stock-based compensation		8,423				8,423
Net income (loss)			(79,237)		(2,154)	(81,391)
Other comprehensive income (loss)				16,788		16,788
Ending balance (in shares) at Dec. 31, 2017	151,650,969
Ending balance at Dec. 31, 2017	$ 15	1,111,432	(683,570)	(887)	22,668	449,658
Increase (Decrease) in Stockholders' Equity
Cumulative effect of adopting ASU (Note 1) \| ASC 606			(1,293)			(1,293)
Adjusted Beginning balance	$ 15	1,111,432	(684,863)	(887)	22,668	448,365
Adjusted Beginning balance (in shares)	151,650,969
Issuance of common stock, net of offering costs (in shares)	51,948,923
Issuance of common stock, net of offering costs	$ 5	81,766				81,771
Stock-based compensation		5,307				5,307
Net income (loss)			(3,790)		(5,393)	(9,183)
Other comprehensive income (loss)				(1,251)		$ (1,251)
Increase in ownership in subsidiary		264			(264)
Ending balance (in shares) at Dec. 31, 2018	203,599,892					203,599,892
Ending balance at Dec. 31, 2018	$ 20	1,198,769	(688,653)	(2,138)	17,011	$ 525,009
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of offering costs (in shares)	1,123,163
Issuance of common stock, net of offering costs		309				309
Stock-based compensation		3,880				3,880
Net income (loss)			20,421		(7,162)	13,259
Other comprehensive income (loss)				572		$ 572
Increase in ownership in subsidiary		228			(228)
Ending balance (in shares) at Dec. 31, 2019	204,723,055					204,723,055
Ending balance at Dec. 31, 2019	$ 20	$ 1,203,186	$ (668,232)	$ (1,566)	$ 9,621	$ 543,029

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ 13,259	$ (9,183)	$ (81,391)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	49,625	51,850	56,614
Provision for doubtful accounts, notes and inventory	2,586	1,857	19,835
Stock-based compensation expense	3,880	5,307	8,123
Change in fair value of derivative instruments	5,545	(9,788)	(46)
Amortization of discount and debt issuance cost	(728)	(1,220)	847
Loss (gain) on disposal of property and equipment	(2,536)	2,554	3,105
Gain on extinguishment of debt, net			(3,195)
Gain from sale of certain assets of subsidiary	(7,455)	(4,782)	(70,658)
Asset impairments and other charges			58,061
Loss from formation of equity method investment		1,163	6,465
Loss from equity method investments	119	2,723	131
Right-of-use asset amortization	3,234
Deferred income taxes	738		(2,400)
Changes in operating assets and liabilities, net of assets and liabilities acquired and disposed:
Accounts and other receivables	(63,408)	(6,360)	6,881
Inventory	3,439	(1,065)	963
Prepaid expenses and other assets	(16,617)	1,547	6,753
Operating lease liabilities	(3,786)
Accounts payable	9,316	679	(8,964)
Deferred revenue	(3,528)	30	9,268
Accrued expenses and other	18,596	2,670	(14,709)
Net cash provided by (used in) operating activities	12,279	37,982	(4,317)
Cash flows from investing activities:
Purchases of short-term investments	(171,080)	(348,091)	(340,194)
Maturities and sales of short-term investments	180,704	425,804	272,220
Purchases of and deposits on property and equipment	(27,088)	(25,263)	(36,307)
Loans made to customers			(894)
Payments on and proceeds from sales of loans receivable	608	518	1,102
Cash received from sale of certain assets of subsidiary, net	7,582	871	149,088
Cash contributed in formation of equity method investment			(2,404)
Investments in other entities			(1,928)
Proceeds from disposal of property and equipment	7,772	530
Net cash provided by (used in) investing activities	(1,502)	54,369	40,683
Cash flows from financing activities:
Issuances of common stock	309	83,438	10,767
Fees paid for issuances of common stock, debt prepayment and debt issuance costs	(123)	(1,004)	(638)
Proceeds from debt instruments and finance lease obligations	15,294	17,243	9,765
Proceeds from revolving line of credit			312
Repayments of borrowing under revolving line of credit			(23,812)
Repayments of debt instruments and finance lease obligations	(7,795)	(194,886)	(30,707)
Payments to holders of stock options in subsidiaries			(8,850)
Net cash provided by (used in) financing activities	7,685	(95,209)	(43,163)
Effect of exchange rates on cash, cash equivalents, and restricted cash	136	274	890
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	18,598	(2,584)	(5,907)
Cash, cash equivalents and restricted cash, beginning of year	34,624	37,208	43,115
Cash, cash equivalents and restricted cash, end of year	53,222	34,624	37,208
Supplemental disclosure of cash flow information:
Income taxes paid	36	257	344
Interest paid, net of $103, $244 and $441 capitalized, respectively	$ 6,788	$ 16,751	$ 17,048

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Cash Flows [Abstract]
Interest paid, capitalized	$ 441	$ 244	$ 103

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

Note 1 —Summary of Significant Accounting Policies

The Company

Clean Energy Fuels Corp., together with its majority and wholly owned subsidiaries (hereinafter collectively referred to as the “Company,” unless the context or the use of the term indicates or requires otherwise) is engaged in the business of selling natural gas as an alternative fuel for vehicle fleets and related natural gas fueling solutions to its customers, primarily in the United States and Canada.

The Company’s principal business is supplying renewable natural gas (“RNG”), compressed natural gas (“CNG”) and liquefied natural gas (“LNG”) (RNG is delivered in the form of CNG or LNG) for light, medium and heavy-duty vehicles and providing operation and maintenance (“O&M”) services for public and private vehicle fleet customer stations. As a comprehensive solution provider, the Company also designs, builds, operates and maintains fueling stations; sells and services natural gas fueling compressors and other equipment used in CNG stations and LNG stations; offers assessment, design and modification solutions to provide operators with code-compliant service and maintenance facilities for natural gas vehicle fleets; transports and sells CNG and LNG via “virtual” natural gas pipelines and interconnects; procures and sells RNG; sells tradable credits it generates by selling RNG and conventional natural gas as a vehicle fuel, including Renewable Identification Numbers (“RIN Credits” or “RINs”) under the federal Renewable Fuel Standard Phase 2 and credits under the California and the Oregon Low Carbon Fuel Standards (collectively, “LCFS Credits”); helps its customers acquire and finance natural gas vehicles; and obtains federal, state and local credits, grants and incentives. In addition, for all periods presented before March 31, 2017, the Company produced RNG at its own production facilities, and for all periods presented before December 29, 2017, the Company manufactured natural gas fueling compressors and other equipment used in CNG stations. See Note 4 for more information.

Basis of Presentation

The accompanying consolidated financial statements include the accounts of the Company and its subsidiaries, and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to state fairly the Company’s consolidated financial position, results of operations, comprehensive loss and cash flows in accordance with accounting principles generally accepted in the United States of America (“US GAAP”). All intercompany accounts and transactions have been eliminated in consolidation.

Reclassifications

The prior period amounts of the current portion of finance lease obligations, $0.7 million, and the long-term portion of finance lease obligations, $3.8 million, have been reclassified to be presented separately in the consolidated balance sheets to conform to the current period presentation. Deferred income taxes of $2.4 million for the year ended December 31, 2017 have been reclassified to be presented separately in the consolidated statements of cash flows to conform to the current year presentation. These reclassifications had no material effect on the Company’s consolidated financial position, results of operations, or cash flows as previously reported.

Use of Estimates

The preparation of consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the amounts reported in the accompanying consolidated financial statements and these notes. Actual results could differ from those estimates and may result in material effects on the Company’s operating results and financial position. Significant estimates made in preparing the accompanying consolidated financial statements include (but are not limited to) those related to revenue recognition, fair value measurements, goodwill and long-lived asset valuations and impairment assessments, income tax valuations and stock-based compensation expense.

Inventory

Inventory consists of raw materials and spare parts, work in process and finished goods and is stated at the lower of cost (first-in, first-out) or net realizable value. The Company evaluates inventory balances for excess quantities and obsolescence by analyzing estimated demand, inventory on hand, sales levels and other information and reduces inventory balances to net realizable value for excess and obsolete inventory based on this analysis.

Inventories consisted of the following as of December 31, 2018 and 2019 (in thousands):


	2018		2019
Raw materials and spare parts	$	34,890	$	29,874
Finished goods		85		—
Total inventory	$	34,975	$	29,874

Derivative Instruments and Hedging Activities

In connection with the Company’s Zero Now truck financing program, the Company entered into commodity swap contracts in October 2018 intended to manage risks related to the diesel-to-natural gas price spread in connection with the natural gas fuel supply commitments the Company expects to make in its anticipated fueling agreements with fleet operators that participate in the Zero Now program. The Company has not designated any derivative instruments as hedges for accounting purposes and does not enter into such instruments for speculative trading purposes. These derivative instruments are recorded in the accompanying consolidated balance sheets and are measured as either an asset or liability at fair value with changes in fair value recognized in earnings. See Note 8 for more information.

Property and Equipment

Property and equipment are recorded at cost. Depreciation and amortization are recognized over the estimated useful lives of the assets using the straight-line method. The estimated useful lives of depreciable assets are three to twenty years for LNG liquefaction plant assets, up to ten years for station equipment and LNG trailers, and three to seven years for all other depreciable assets. Leasehold improvements are amortized over the shorter of their estimated useful lives or related lease terms. Periodically, the Company receives grant funding to assist in the financing of natural gas fueling station construction. The Company records the grant proceeds as a reduction of the cost of the respective asset. Total grant proceeds received were approximately $4.4 million, $0.7 million, and $1.6 million for the years ended December 31, 2017, 2018, and 2019, respectively.

Long-Lived Assets

The Company reviews the carrying value of its long-lived assets, including property and equipment and intangible assets with finite useful lives, for impairment whenever events or changes in circumstances indicate that the carrying value of an asset or asset group may not be recoverable. Events that could result in an impairment review include, among others, a significant decrease in the operating performance of a long-lived asset or asset group or the decision to close a fueling station. Impairment testing involves a comparison of the sum of the undiscounted future cash flows of the asset or asset group to its carrying amount. If the sum of the undiscounted future cash flows exceeds the carrying amount, then no impairment exists. If the carrying amount exceeds the sum of the undiscounted future cash flows, then a second step is performed to determine the amount of impairment, if any, to be recognized. An impairment loss is recognized to the extent that the carrying amount of the asset or asset group exceeds its fair value. The fair value of the asset or asset group is based on estimated discounted future cash flows of the asset or asset group using a discount rate commensurate with the related risk. The estimate of future cash flows requires management to make assumptions and to apply judgment, including forecasting future sales and expenses and estimating useful lives of the assets. These estimates can be affected by a number of factors, including, among others, future results, demand, and economic conditions, many of which can be difficult to predict.

There were no impairments of the Company’s long-lived assets in the years ended December 31, 2018 and 2019. In the third quarter of the year ended December 31, 2017, the Company recorded asset impairment charges of $32.3 million related to its then-subsidiary, IMW Industries Ltd. (“IMW”) (formerly known as Clean Energy Compression Corp.) (“CEC”) and $20.4 million related to certain station closures (see Note 3 for more information).

Intangible assets with finite useful lives are amortized over their respective estimated useful lives using the straight-line method. The estimated useful lives of intangible assets with finite useful lives are from one to eight years for customer relationships, one to ten years for acquired contracts, two to ten years for trademarks and trade names, and three years for non-compete agreements.

The Company’s intangible assets as of December 31, 2018 and 2019 were as follows (in thousands):


	2018		2019
Customer relationships	$	5,376	$	5,376
Acquired contracts		4,384		4,384
Trademark and trade names		2,700		2,700
Non-compete agreements		860		860
Total intangible assets		13,320		13,320
Less accumulated amortization		(11,113)		(12,091)
Net intangible assets	$	2,207	$	1,229

Amortization expense for intangible assets was $5.1 million, $1.4 million, and $1.0 million for the years ended December 31, 2017, 2018, and 2019, respectively. Estimated amortization expense for the two years succeeding the year ended December 31, 2019 is approximately $0.8 million in 2020 and $0.5 million in 2021.

Goodwill

Goodwill represents the excess of costs incurred over the fair value of the net assets of acquired businesses. The Company assesses its goodwill using either a qualitative or quantitative approach to determine whether it is more likely than not that the fair value of its reporting unit is less than its carrying value. The Company is required to use judgment when applying the goodwill impairment test, including, among other considerations, the identification of reporting unit(s), the assessment of qualitative factors, and the estimation of fair value of a reporting unit in the quantitative approach. The Company determined that it is a single reporting unit for the purpose of goodwill impairment tests. The Company performs the impairment test annually on October 1, or more frequently if facts and circumstances warrant a review.

The qualitative goodwill assessment includes the potential impact on a reporting unit’s fair value of certain events and circumstances, including its enterprise value, macroeconomic conditions, industry and market considerations, cost factors, and other relevant entity-specific events. If it is determined, based upon the qualitative assessment, that it is more likely than not that the reporting unit’s fair value is less than its carrying amount, then a quantitative impairment test is performed.

The quantitative assessment estimates the reporting unit’s fair value based on its enterprise value plus an assumed control premium as evidence of fair value. The estimates used to determine the fair value of the reporting unit may change based on results of operations, macroeconomic conditions, stock price fluctuations, or other factors. Changes in these estimates could materially affect our assessment of the fair value and goodwill impairment for the reporting unit.

During the years ended December 31, 2018 and 2019, the Company utilized the quantitative approach and concluded there were no indicators of impairment to goodwill.

During the third quarter of the year ended December 31, 2017, as a result of the asset impairment charges recorded for intangible assets and stations (described previously and in Note 3), the Company determined that sufficient indicators of potential impairment existed to require an interim goodwill test of its one reporting unit prior to the annual test performed in the fourth quarter of 2017. The goodwill test was performed by computing the fair value of the reporting unit and comparing it to the carrying value using a quantitative assessment. Based on the results of the goodwill test, the Company concluded that it was more likely than not that the fair value of its reporting unit exceeded its carrying amount and thus no impairment existed. The annual impairment test was subsequently performed on October 1 using the quantitative assessment and the Company concluded no impairment existed.

The following table summarizes the activity related to the carrying amount of goodwill (in thousands):


Balance as of December 31, 2017	$	64,328
Balance as of December 31, 2018	$	64,328
Balance as of December 31, 2019	$	64,328

Revenue Recognition

On January 1, 2018, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASC 606”), using the modified retrospective method and recognized the cumulative effect of initially applying ASC 606 as an adjustment to “Accumulated deficit” as of January 1, 2018. The reported results for the years ended December 31, 2018 and 2019 are presented under ASC 606, while the reported results for periods prior to January 1, 2018 are not adjusted and were prepared in accordance with ASC 605, Revenue Recognition. The adoption of ASC 606 did not have a material impact on the Company’s consolidated financial statements.

The ASC 606 adoption adjustments are as follows, and relate to significant financing components resulting from an advance payment by a customer of the Company’s subsidiary, NG Advantage LLC (“NG Advantage”) and an extended payment term to a station construction customer (in thousands):


	Balance as of		Adjustments		Balance as of
	December 31, 2017		due to ASC 606		January 1, 2018
Notes receivable and other long-term assets, net	$	21,397	$	(963)	$	20,434
Deferred revenue	$	3,432	$	330	$	3,762
Accumulated deficit	$	(683,570)	$	(1,293)	$	(684,863)

The Company recognizes revenue when control of the promised goods or services is transferred to its customers, in an amount that reflects the consideration to which it expects to be entitled in exchange for the goods or services. In order to achieve that core principle, a five-step approach is applied: (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue allocated to each performance obligation when the Company satisfies the performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account for revenue recognition.

The Company is generally the principal in its customer contracts because it has control over the goods and services prior to them being transferred to the customer, and as such, revenue is recognized on a gross basis. Sales and usage-based taxes are excluded from revenues. Revenue is recognized net of allowances for returns and any taxes collected from customers, which are subsequently remitted to governmental authorities.

Volume-Related

The Company’s volume-related revenue primarily consists of sales of RNG, CNG and LNG fuel, O&M services and RINs and LCFS Credits in addition to changes in fair value of the Company’s derivative instruments associated with providing natural gas to customers under fueling contracts.

Fuel and O&M services are sold pursuant to contractual commitments over defined goods-and-service delivery periods. These contracts typically include a stand-ready obligation to supply natural gas and/or provide O&M services daily based on a committed and agreed upon routine maintenance schedule or when and if called upon by the customer.

The Company applies the ‘right to invoice’ practical expedient and recognizes fuel and O&M services revenue in the amount to which the Company has the right to invoice. The Company has a right to consideration based on the amount of gasoline gallon equivalents of natural gas dispensed by the customer and current pricing conditions, which are typically billed to the customer on a monthly basis. Since payment terms are less than a year, the Company has elected the practical expedient which allows it to not assess whether a customer contract has a significant financing component.

Contract modifications are not distinct from the existing contract and are typically renewals of fuel and O&M service sales. As a result, these modifications are accounted for as if they were part of the existing contract. The effect of a contract modification on the transaction price is recognized prospectively.

The Company sells RINs and LCFS Credits to third parties that need the credits to comply with federal and state requirements. Revenue is recognized on these credits when there is an agreement in place to monetize the credits at a determinable price.

The changes in fair value of derivative instruments relate to the Company’s commodity swap and customer fueling contracts. The contracts are measured at fair value with changes in the fair value recorded in the accompanying consolidated statements of operations in the period incurred. The amounts are classified as revenue because the Company’s commodity swap contracts are used to economically offset the risk associated with the diesel-to-natural gas price spread resulting from anticipated customer fueling contracts under the Company’s Zero Now truck financing program. See Note 8 for more information about these derivative instruments. For the years ended December 31, 2018 and 2019, changes in the fair value of commodity swaps and customer contracts amounted to a gain of $10.3 million and a loss of $(6.6) million, respectively. No amounts were recognized in 2017 as the inception of these arrangements was October 2018.

Station Construction Sales

Station construction contracts are generally short-term, except for certain larger and more complex stations, which can take up to 24 months to complete. For most of the Company’s station construction contracts, the customer contracts with the Company to provide a significant service of integrating a complex set of tasks and components into a single station. Hence, the entire contract is accounted for as one performance obligation.

The Company recognizes revenue over time as the Company performs under its station construction contracts because of the continual transfer of control of the goods to the customer, who typically controls the work in process. Revenue is recognized based on the extent of progress towards completion of the performance obligation and is recorded proportionally as costs are incurred. Costs to fulfill the Company’s obligations under these contracts typically include labor, materials and subcontractors’ costs, other direct costs and an allocation of indirect costs.

Refinements of estimates to account for changing conditions and new developments are continuous and characteristic of the process. Many factors that can affect contract profitability may change during the performance period of the contract, including differing site conditions, the availability of skilled contract labor, the performance of major suppliers and subcontractors, and unexpected changes in material costs. Because a significant change in one or more of these estimates could affect the profitability of these contracts, the contract price and cost estimates are reviewed periodically as work progresses and adjustments proportionate to the cost-to-cost measure of progress are reflected in contract revenues in the reporting period when such estimates are revised as discussed above. Provisions for estimated losses on uncompleted contracts are recorded in the period in which the losses become known.

Contract modifications are typically expansions in scope of an existing station construction project. As a result, these modifications are accounted for as if they were part of the existing contract. The effect of a contract modification on the transaction price and the Company’s measure of progress for the performance obligation to which it relates is recognized as an adjustment to revenue (either as an increase or a reduction) on a cumulative catch-up basis.

Under the typical payment terms of the Company’s station construction contracts, the customer makes either performance-based payments (“PBPs”) or progress payments. PBPs are interim payments of the contract price based on quantifiable measures of performance or the achievement of specified events or milestones. Progress payments are interim payments of costs incurred as the work progresses. For some of these contracts, the Company may be entitled to receive an advance payment. The advance payment typically is not considered a significant financing component because it is used to meet working capital demands that can be higher in the early stages of a construction contract and to protect the Company if the customer fails to adequately complete some or all of its obligations under the contract. In addition, the customer retains a small portion of the contract price until completion of the contract. Such retained portion of the contract price is not considered a significant financing component because the intent is to protect the customer.

In certain contracts with its customers, the Company agrees to provide multiple goods or services, including construction of and sale of a station, O&M services, and sale of fuel to the customer. These contracts have multiple performance obligations because the promise to transfer each separate good or service is separately identifiable and is distinct. This evaluation requires significant judgment and the decision to combine a group of contracts or separate the combined or single contract into multiple performance obligations could change the amount of revenue recognized in one or more periods.

The Company allocates the contract price to each performance obligation using best estimates of the standalone selling price of each distinct good or service in the contract. The primary method used to estimate the standalone selling price for fuel and O&M services is observable standalone sales, and the primary method used to estimate the standalone selling price for station construction sales is the expected cost plus a margin approach because the Company sells customized customer-specific solutions. Under this approach, the Company forecasts expected costs of satisfying a performance obligation and then adds an appropriate margin for the good or service.

AFTC

See discussion under “Alternative Fuels Tax Credit” below for more information about AFTC, which is not recognized as revenue until the period the credit is authorized through federal legislation.

Other

The majority of other revenue is from sales of used natural gas heavy-duty trucks purchased by the Company. Revenue on these contracts is recognized at the point in time when the customer accepts delivery of the truck.

Alternative Fuels Tax Credit

Under separate pieces of U.S. federal legislation, the Company has been eligible to receive a federal alternative fuels tax credit (“AFTC”) for its natural gas vehicle fuel sales made between October 1, 2006 and December 31, 2019. The AFTC, which had previously expired on December 31, 2016, was reinstated on February 9, 2018 to apply retroactively to vehicle fuel sales made from January 1, 2017 through December 31, 2017. On December 20, 2019, AFTC was retroactively extended beginning January 1, 2018 through December 31, 2020. The AFTC credit is equal to $0.50 per gasoline gallon equivalent of CNG that the Company sold as vehicle fuel, and $0.50 per diesel gallon of LNG that the Company sold as vehicle fuel in 2017, 2018 and 2019.

Based on the service relationship with its customers, either the Company or its customer claims the credit. The Company records its AFTC credits, if any, as revenue in its consolidated statements of operations because the credits are fully payable to the Company and do not offset income tax liabilities. As such, the credits are not deemed income tax credits under the accounting guidance applicable to income taxes.

As a result of the most recent legislation authorizing AFTC being signed into law on December 20, 2019, all AFTC revenue for vehicle fuel the Company sold in the 2018 and 2019 calendar years, totaling $47.1 million, was recognized during the year ended December 31, 2019. As a result of the previous legislation authorizing AFTC being signed into law on February 9, 2018, all AFTC revenue for vehicle fuel the Company sold in the 2017 calendar year, totaling $25.2 million, was recognized and collected during the year ended December 31, 2018. In addition, during the year ended December 31, 2018, the Internal Revenue Service (“IRS”) approved, and the Company recognized as revenue, $1.5 million of AFTC credit claims related to prior years. The Company recognized no AFTC revenue for the year ended December 31, 2017. AFTC is currently available through December 31, 2020 and may not be reinstated for vehicle fuel sales made after that date.

LNG Transportation Costs

The Company records the costs incurred to transport LNG to its customers in “Product cost of sales” in the accompanying consolidated statements of operations.

Advertising Costs

Advertising costs are expensed as incurred. Advertising costs were $0.3 million, $0.9 million and $1.2 million for the years ended December 31, 2017, 2018, and 2019, respectively.

Stock-Based Compensation

The Company recognizes compensation expense for all stock‑based payment arrangements over the requisite service period of the award. For stock options, the Company determines the grant date fair value using the Black‑Scholes option pricing model, which requires the input of certain assumptions, including the expected life of the stock‑based payment award, stock price volatility and risk‑free interest rate. For restricted stock units, the Company determines the grant date fair value based on the closing market price of its common stock on the date of grant.

In March 2016, the FASB issued ASU 2016‑09, Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payments Accounting, which simplified the accounting for share-based payment transactions. The Company adopted the standard as of January 1, 2017 and in connection with the adoption, elected to recognize forfeitures when they occur. This election was implemented under the modified retrospective approach with a cumulative effect of an increase in accumulated deficit of $0.2 million, net of tax. This adjustment represents the cumulative additional compensation expense that would have been recognized through the date of adoption

Income Taxes

Income taxes are computed using the asset and liability method. Under this method, deferred income taxes are recognized by applying enacted statutory tax rates applicable to future years to differences between the tax bases and financial carrying amounts of existing assets and liabilities. The impact on deferred taxes of changes in tax rates and laws, if any, are applied to the years during which temporary differences are expected to be settled and are reflected in the consolidated financial statements in the period of enactment. Valuation allowances are established when management determines it is more likely than not that deferred tax assets will not be realized. When evaluating the need for a valuation analysis, we use estimates involving a high degree of judgment including projected future US GAAP income and the amounts and estimated timing of the reversal of any deferred tax assets and liabilities.

The Company has a recognition threshold and a measurement attribute for the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. For those benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities based on the technical merits of the position. The amount recognized is measured as the largest amount of benefit that has a greater than 50 percent likelihood of being realized upon ultimate settlement. The Company recognizes potential accrued interest and penalties related to unrecognized tax benefit in income tax expense.

The Company operates within multiple domestic and foreign taxing jurisdictions and is subject to audit in these jurisdictions. These audits can involve complex issues, which may require an extended period of time to resolve. Although the Company believes that adequate consideration has been given to these issues, it is possible that the ultimate resolution of these issues could be significantly different from originally estimated.

In October 2016, the FASB issued ASU 2016‑16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. Under the new standard, the selling (transferring) entity is required to recognize a current tax expense or benefit upon transfer of the asset. Similarly, the purchasing (receiving) entity is required to recognize a deferred tax asset or liability, as well as the related deferred tax benefit or expense, upon purchase or receipt of the asset. The Company early adopted the standard as of January 1, 2017. This election was implemented under the modified retrospective approach, resulting in a $0.3 million increase in accumulated deficit representing the cumulative recognition of the income tax consequences of intra-entity transfers of assets other than inventory that occurred before the adoption date.

Net Income (Loss) Per Share

Basic net income (loss) per share is computed by dividing the net income (loss) attributable to Clean Energy Fuels Corp. by the weighted-average number of common shares outstanding and common shares issuable for little or no cash consideration during the period. Diluted net income (loss) per share is computed by dividing the net loss attributable to Clean Energy Fuels Corp. by the weighted-average number of common shares outstanding and common shares issuable for little or no cash consideration during the period and potentially dilutive securities outstanding during the period, and therefore reflects the dilution from common shares that may be issued upon exercise or conversion of these potentially dilutive securities, such as stock options, warrants, convertible notes and restricted stock units. The dilutive effect of stock awards and warrants is computed under the treasury stock method. The dilutive effect of convertible notes and restricted stock units is computed under the if-converted method. Potentially dilutive securities are excluded from the computations of diluted net income (loss) per share if their effect would be antidilutive.

Foreign Currency Translation and Transactions

The Company uses the local currency as the functional currency of its foreign subsidiary and equity method investment. Accordingly, all assets and liabilities outside the United States are translated into U.S. dollars at the rate of exchange in effect at the balance sheet date. Revenue and expense items are translated at the weighted-average exchange rates prevailing during the period. Foreign currency translation adjustments are recorded as accumulated other comprehensive income (loss) in stockholders’ equity.

Foreign currency transactions occur when there is a transaction denominated in other than the respective entity’s functional currency. The Company records the changes in the exchange rate for these transactions in its consolidated statements of operations. For the years ended December 31, 2017, 2018, and 2019, foreign exchange transaction gains and (losses) were included in “Other income (expense), net” in the accompanying consolidated statements of operations and were $(0.2) million, $(0.0) million and $0.0 million, respectively.

Comprehensive Income (Loss)

Comprehensive income (loss) is defined as the change in equity (net assets) of a business enterprise during the period from transactions and other events and circumstances from non-owner sources. The difference between net income (loss) and comprehensive income (loss) for the years ended December 31, 2017, 2018, and 2019 was comprised of the Company’s foreign currency translation adjustments and unrealized gains and losses on available-for-sale securities.

Concentration of Credit Risk

Credit is extended to all customers based on financial condition, and collateral is generally not required. Concentrations of credit risk with respect to trade receivables are limited because of the large number of customers comprising the Company’s customer base and dispersion across many different industries and geographies. Certain international customers, however, have historically been slower to pay on trade receivables. Accordingly, the Company continually monitors collections and payments from its customers and maintains a provision for estimated credit losses based upon its historical experience and any specific customer collection issues that it has identified. Although credit losses have historically been within the Company’s expectations and the provisions established, the Company cannot guarantee that it will continue to experience the same credit loss rates that it has in the past.

Recently Adopted Accounting Changes and Recently Issued Accounting Standards

Recently Adopted Accounting Changes

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASC 842”), which amends the guidance in former Accounting Standards Codification Topic 840, Leases (“ASC 840”). The new standard requires most leases to be recognized on the balance sheet, which will increase reported assets and liabilities. Accounting for lessors and capital leases (now known as finance leases) is substantially similar to ASC 840. The new standard is effective for annual and interim periods in fiscal years beginning after December 15, 2018, which for the Company was the first quarter of 2019.

The Company adopted this standard using the modified retrospective transition method. Results for reporting periods beginning after January 1, 2019 are presented under ASC 842, while prior period amounts are not adjusted. This adoption had a material effect on the Company’s consolidated balance sheets as a result of recording ROU assets and lease liabilities for existing operating leases on the consolidated balance sheets. The adoption did not have a material effect on the Company’s consolidated statements of operations or its consolidated statements of cash flows.

As permitted under ASC 842, the Company elected the package of practical expedients that permit it to not reassess (1) whether an existing contract is or contains a lease, (2) the classification of existing leases, and (3) whether previously capitalized costs continue to qualify as initial indirect costs. The Company also elected the practical expedient allowing it to use hindsight in determining the lease term and in assessing the likelihood a purchase option will be exercised.

The effect of adopting ASC 842 was as follows (in thousands):


	Balance as of		Adjustments		Balance as of
	December 31, 2018		Due to ASC 842		January 1, 2019
Operating lease right-of-use assets	$	—	$	24,453	$	24,453
Operating lease obligations	$	—	$	25,943	$	25,943
Accrued liabilities	$	48,469	$	(496)	$	47,973
Other long-term liabilities	$	15,035	$	(994)	$	14,041

Recently Issued Accounting Standards

In June 2016, the FASB issued ASU No. 2016‑13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The new standard amends the impairment model to utilize an expected loss methodology in place of the currently used incurred loss methodology, which will result in the more timely recognition of losses. This pronouncement is effective for reporting periods beginning after December 15, 2019. The Company will adopt this standard in the first quarter of 2020. The Company does not expect adoption of this ASU to have a material impact on its consolidated financial statements and related disclosures.

Revenue

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

Revenue

Note 2 —Revenue from Contracts with Customers

Disaggregation of Revenue

The table below presents the Company’s revenue disaggregated by revenue source (in thousands):


	Years Ended December 31,
	2017		2018		2019
Volume-related (1)	$	264,880	$	286,684	$	273,535
Station construction sales		51,854		25,501		23,120
AFTC		—		26,729		47,123
Compressor sales (2)		23,527		—		—
Other		1,338		7,505		287
Total revenue	$	341,599	$	346,419	$	344,065

(1) Includes changes in fair value of derivative instruments related to the Company’s commodity swap and customer fueling contracts. See Note 1 and Note 8 for more information about these derivative instruments. For the years ended December 31, 2018 and 2019, changes in the fair value of commodity swaps and customer fueling contracts amounted to a gain of $10.3 million and a loss of $6.6 million, respectively.

(2) The Company completed the CEC Combination (as defined in Note 4) during the year ended December 31, 2017 and no longer generates revenue from compressor sales.

Remaining Performance Obligations

Remaining performance obligations represent the transaction price of customer orders for which the work has not been performed. As of December 31, 2019, the aggregate amount of the transaction price allocated to remaining performance obligations was $15.8 million, which related to the Company’s station construction sale contracts. The Company expects to recognize revenue on the remaining performance obligations under these contracts over the next 12 to 24 months.

For volume-related revenue, the Company has elected to apply an optional exemption, which waives the requirement to disclose the remaining performance obligation for revenue recognized through the ‘right to invoice’ practical expedient.

Costs to Fulfill a Contract

The Company capitalizes costs incurred to fulfill its contracts that (1) relate directly to the contract, (2) are expected to generate resources that will be used to satisfy the Company’s performance obligations under the contract, and (3) are expected to be recovered through revenue generated under the contract. Contract fulfillment costs are recorded to depreciation expense as the Company satisfies its performance obligations over the term of the contract. These costs primarily relate to set-up and other direct installation costs incurred by NG Advantage, for equipment that must be installed on customers’ land before NG Advantage, LLC (“NG Advantage”) is able to deliver CNG to the customer because the customer does not have direct access to the natural gas pipelines. These costs are classified in “Land, property, and equipment, net” in the accompanying consolidated balance sheets. As of December 31, 2018 and 2019, these capitalized costs incurred to fulfill contracts were $9.1 million and $10.2 million with accumulated depreciation of $4.9 million and $6.3 million, respectively, and related depreciation expense of $2.0 million and $2.2 million for the years ended December 31, 2018 and 2019, respectively.

Contract Balances

The timing of revenue recognition, billings and cash collections results in billed accounts receivable, unbilled receivables (contract assets), and customer advances and deposits (contract liabilities) in the accompanying consolidated balance sheets. Changes in the contract asset and liability balances during the year ended December 31, 2019, were not materially affected by any factors outside the normal course of business.

As of December 31, 2018 and 2019, the Company’s contract balances were as follows (in thousands):


	2018		2019
Accounts receivable, net	$	68,865	$	61,760

Contract assets - current	$	656	$	455
Contract assets - non-current		3,825		3,777
Contract assets - total	$	4,481	$	4,232

Contract liabilities - current	$	5,513	$	5,329
Contract liabilities - non-current		9,844		6,339
Contract liabilities - total	$	15,357	$	11,668

Accounts Receivable, Net

“Accounts receivable, net” in the accompanying consolidated balance sheets include amounts billed and currently due from customers. The amounts due are stated at their net estimated realizable value. The Company maintains an allowance for doubtful accounts to provide for the estimated amount of receivables that will not be collected. The allowance is based upon an assessment of customer creditworthiness, historical payment experience, and the age of outstanding receivables.

Contract Assets

Contract assets include unbilled amounts typically resulting from the Company’s station construction sale contracts, when the cost-to-cost method of revenue recognition is utilized and revenue recognized exceeds the amount billed to the customer, and right to payment is not just subject to the passage of time. Amounts may not exceed their net realizable value. Contract assets are classified as current or noncurrent based on the timing of billings. The current portion is included in “Prepaid expenses and other current assets” and the noncurrent portion is included in “Notes receivable and other long-term assets, net” in the accompanying consolidated balance sheets.

Contract Liabilities

Contract liabilities consist of billings in excess of revenue recognized from the Company’s station construction sale contracts and payments primarily from a customer of NG Advantage in advance of the performance obligations. Billings in excess of revenue recognized of $2.0 million and $1.8 million and advance payments of $3.5 million and $3.5 million are classified as current as of December 31, 2018 and 2019, respectively. Deferred revenue is classified as current or noncurrent based on when the revenue is expected to be recognized. The current portion and noncurrent portion of deferred revenue are included in “Deferred revenue” and “Other long-term liabilities,” respectively, in the accompanying consolidated balance sheets.

The increase in the contract liabilities balance for the year ended December 31, 2019 is primarily driven by billings in excess of revenue recognized, offset by $5.9 million of revenue recognized related to the Company’s contract liability balances as of December 31, 2018.

Asset Impairments, Other Charges, and Inventory Valuation Provision

12 Months Ended

Dec. 31, 2019

Restructuring and Related Activities [Abstract]

Asset Impairments, Other Charges, and Inventory Valuation Provision

Note 3 —Asset Impairments, Other Charges, and Inventory Valuation Provision

In light of continued low oil prices and the state of natural gas vehicle adoption, among other factors, during the third quarter of the year ended December 31, 2017, the Company undertook an evaluation of its operations with the intent of minimizing and eliminating assets it believed were underperforming. As a result of this evaluation, the Company identified certain of its fueling stations where the current and projected natural gas volume and profitability levels were not expected to be sufficient to support the Company’s investment in the fueling station assets, and the Company decided to close these stations. The Company also reduced its workforce and took other steps to reduce overhead costs as a result of this evaluation, in an effort to lower its operating expenses going forward. In addition, this evaluation resulted in a strategic shift in how the Company viewed its natural gas compressor manufacturing business, operated by CEC. In an effort to increase the scale and reach and improve the financial prospects of the Company’s investment in this business, the Company entered into an investment agreement with a strategic partner in November 2017, pursuant to which both parties combined their respective natural gas compressor manufacturing businesses (see Note 4 for more information). As a result of these decisions and the steps taken to implement them, during the year ended December 31, 2017, the Company incurred on a pre-tax basis, aggregate cash and non-cash charges related to asset impairments and other charges, and a non-cash inventory valuation charge. In addition, the Company incurred a cash charge for payments made as a result of temporary restrictions on its LCFS Credits account during the fourth quarter of 2017.

The following table summarizes these charges (in thousands):


	Year Ended
	December 31, 2017
Workforce reduction and related charges	$	3,057
CEC asset impairments		32,274
Station closures and related charges		25,557
LCFS Credits charge		7,046
Total asset impairments and other charges		67,934
Inventory valuation provision		13,158
Total charges	$	81,092

Cash Charges

The following table summarizes the charges related to the foregoing that have been or will be settled with cash payments and their related liability balances as of December 31, 2018 and 2019 (in thousands):


			Cash Payments			Cash Payments				Cash Payments
			Made in the			Made in the				Made in the
			Year Ended	Balance as of		Year Ended		Balance as of		Year Ended		Balance as of
	Charges		December 31, 2017	December 31, 2017		December 31, 2018		December 31, 2018		December 31, 2019		December 31, 2019
Employee severance	$	2,757	(2,757)	$	—	$	—	$	—	$	—	$	—
Lease termination fees and AROs for station closures		4,083	(70)		4,013		(1,810)		2,203		(249)		1,954
	$	6,840	(2,827)	$	4,013	$	(1,810)	$	2,203	$	(249)	$	1,954

Workforce Reduction and Related Charges

As a result of the workforce reduction in 2017, severance costs of $2.8 million were incurred in connection with employee terminations and $0.3 million in stock-based compensation expense was incurred for the associated acceleration of certain stock awards.

Impairments of Long-Lived Assets

CEC: Asset Impairment Charges

Due to the continued low global demand for compressors, and the decision to position CEC’s compressor manufacturing business for industry consolidation with a potential strategic partner, the Company’s management determined that an impairment indicator was present for the long-lived assets of CEC. Recoverability was tested using future cash flow projections based on management’s long-term estimates of market conditions. Based on the results of this test, the sum of the undiscounted future cash flows was less than the carrying value of the CEC asset group. As a result, these long-lived assets were written down to their respective fair values, resulting in an impairment charge of $32.3 million. Fair value was based on expected future cash flows using Level 3 inputs. The cash flows are those expected to be generated by market participants, discounted at an appropriate rate for the risks inherent in those cash flow projections.

Station Closures and Related Charges

During the third quarter of the year ended December 31, 2017, the Company decided to close 42 fueling stations by December 31, 2017, which were performing below management’s expectations based on volume and profitability levels. As a result, these station assets, which had an aggregate carrying value of $23.3 million, were written down to their respective fair values of $2.9 million on an aggregate basis, resulting in a charge of $20.4 million. The fair values of these assets were determined using the cost approach.

In addition, certain of these station closures triggered related other charges totaling $5.2 million, which consisted of write-offs for any deferred losses, lease termination fees, and an increase in asset retirement obligations (“AROs”).

Due to the closure of these stations, the Company’s management assessed whether impairment indicators were present for the long-lived assets of the Company’s other fueling stations. The Company determined there were no indicators of impairment present among its remaining fueling stations and no further steps were required for an impairment evaluation with respect to these stations.

Inventory Valuation Provision

As a result of the Company’s evaluation process to minimize and eliminate underperforming station assets, the Company determined that $27.2 million of certain station parts which were historically classified as construction in progress within “Land, property, and equipment, net” were to be reclassified as “Inventory” in the accompanying consolidated balance sheets because they will primarily be used for stations to be sold. Subsequent to the reclassification, the Company calculated and recorded a lower of cost or market non-cash charge of $7.8 million for these station parts. Additionally, in conjunction with its decision to seek a strategic partner for CEC, the Company incurred a lower of cost or market non-cash charge of $5.4 million for the inventory of CEC. The aggregate amount of $13.2 million is reported as “Inventory valuation provision” in the accompanying consolidated statements of operations for the year ended December 31, 2017.

LCFS Credits Cash Payments

The Company generates LCFS Credits when it sells RNG and conventional natural gas for use as a vehicle fuel and can sell and transfer these credits to third parties. The California Air Resources Board (“CARB”) restricted the Company’s ability to sell and transfer LCFS Credits during the third and fourth quarters of 2017 pending completion of an administrative review. The Company was, however, required to settle preexisting contractual obligations to transfer LCFS Credits to third parties by making cash payments totaling $7.0 million, the equivalent value of the LCFS Credits the Company would have otherwise transferred to satisfy its obligations. These payments are reported in “Asset impairments and other charges” in the accompanying consolidated statements of operations for the year ended December 31, 2017. In November 2017, CARB invalidated certain LCFS Credits the Company had generated in prior periods and released the restriction on the Company’s ability to sell and transfer LCFS Credits.

Divestitures	12 Months Ended
Divestitures	Dec. 31, 2019
Business Combinations [Abstract]
Divestitures	Note 4 —Divestitures BP Transaction On February 27, 2017, Clean Energy Renewable Fuels (“Renewables”) entered into an asset purchase agreement (the “APA”) with BP Products North America (“BP”). Pursuant to the APA, Renewables agreed to sell to BP its assets relating to its RNG production business (the “BP Transaction”), consisting of Renewables’ two RNG production facilities, Renewables’ interest in joint ventures formed with a third-party to develop new RNG production facilities, and Renewables’ third-party RNG supply contracts (the “Assets”). The BP Transaction was completed on March 31, 2017 for a sale price of $155.5 million, plus BP assumed $8.8 million of debt. On March 31, 2017, BP paid Renewables $30.0 million in cash and delivered to Renewables a promissory note with a principal amount of $123.5 million, which was paid in full on April 3, 2017. In addition, as a result of the determination of certain post-closing adjustments, (i) BP paid Renewables an additional $2.0 million on June 22, 2017, and (ii) the gain recorded from the BP Transaction was reduced by $0.8 million. Pursuant to the APA, the valuation date of the BP Transaction was January 1, 2017, and as a result, the APA included certain adjustments to the purchase price to reflect a determination of the amount of cash accumulated by Renewables from the valuation date to the closing date, net of permitted cash outflows. Control of the Assets was not transferred until the BP Transaction was completed on March 31, 2017. Accordingly, the full operating results of Renewables are included in the accompanying consolidated statements of operations through March 31, 2017. The net cash proceeds from the BP Transaction were $142.2 million, net of $1.0 million cash transferred to BP, and the Company incurred $3.7 million in transaction fees in connection with the BP Transaction. The BP Transaction resulted in a total gain of $70.7 million, which was recorded in “Gain from sale of certain assets of subsidiary” in the accompanying consolidated statements of operations for the year ended December 31, 2017. Included in the determination of this gain amount is goodwill of $26.6 million allocated to the disposed assets based on the relative fair values of the assets disposed and the portion of the retained reporting unit. The Company determined that the BP Transaction did not meet the definition of a discontinued operation because the disposal did not represent a strategic shift that will have a major effect on the Company’s operations and financial results. In addition, under the APA, BP is required, following the closing of the BP Transaction, to pay Renewables up to an additional $25.0 million in cash over a five-year period if certain conditions relating to the Assets are met. In February 2018, the Company received $0.9 million in cash for its satisfaction of the performance criteria for the first period under the APA, which ended on December 31, 2017. Upon its receipt of such cash, the Company paid $0.1 million in cash and issued 15,877 shares of the Company’s common stock with a fair value of $0.0 million to former holders of options to purchase membership units in Renewables. The performance criteria for the second period under the APA, which ended on December 31, 2018, was also satisfied, and the Company received a cash payment of $5.4 million in March 2019. During the year ended December 31, 2019, after receipt of the cash payment, the Company paid $0.6 million in cash to former holders of options to purchase membership units in Renewables. In December 2019, the Company and BP entered into an Amendment to the APA (“Amended APA”) which amended the earn-out for years four and five and paid the Company an additional $2.8 million for year three of the earn-out period. As a result of the performance criteria for year three under the APA being satisfied, and the additional $2.8 million received by the Company in December 2019 in accordance with the Amended APA, the Company recognized a gross gain of $8.4 million and accrued amounts due to former holders of options to purchase membership units in Renewables of $0.9 million as of December 31, 2019. The Company recognized a net gain of $0.8 million, $4.8 million, and $7.5 million during the years ended December 31, 2017, 2018 and 2019, respectively, which is included in “Gain from sale of certain assets of subsidiary” in the accompanying consolidated statements of operations. The net gain of $0.8 million during the year ended December 31, 2017 is included in the total gain on the BP Transaction stated above. As of December 31, 2019, the Company has paid $9.2 million in cash and issued 770,269 shares of the Company’s common stock with a fair value of $2.0 million to former holders of options to purchase membership units in Renewables. Following the completion of the BP Transaction, Renewables and the Company continue to procure RNG from BP under a long-term supply contract (the “BP Supply Agreement”) and from other RNG suppliers, and resell such RNG through the Company’s natural gas fueling infrastructure as Redeem, the Company’s RNG vehicle fuel. On October 1, 2018, Renewables and BP amended the BP Supply Agreement to extend the term and add additional RNG supply. BP and Renewables share in the RINs and LCFS Credits generated from the increased RNG supply sold through the Company’s vehicle fueling infrastructure and to other customers. See Note 2 for information on revenue recognition of these credits. SAFE&CEC S.r.l. On November 26, 2017, the Company, through its former subsidiary, CEC, entered into an investment agreement with Landi Renzo S.p.A. (“LR”), an alternative fuels company based in Italy. Pursuant to the investment agreement, the Company and LR agreed to combine their respective natural gas compressor subsidiaries, CEC and SAFE S.p.A, in a new company known as “SAFE&CEC S.r.l.” (such combination transaction is referred to as the “CEC Combination”). SAFE&CEC S.r.l. is focused on manufacturing, selling and servicing natural gas fueling compressors and related equipment for the global natural gas fueling market. Upon the closing of the CEC Combination on December 29, 2017, the Company owns 49% of SAFE&CEC S.r.l. and LR owns 51% of SAFE&CEC S.r.l. The Company accounts for its interest in SAFE&CEC S.r.l. using the equity method of accounting because the Company does not control but has the ability to exercise significant influence over SAFE&CEC S.r.l.’s operations. The fair value of the CEC Combination was determined using the income valuation approach. Under the income approach, the Company used a discounted cash flow model (“DCF”) in which cash flows anticipated over several periods, plus a terminal value at the end of that time horizon, are discounted to their present value using an appropriate expected discount rate. The discount rate used for cash flows reflects capital market conditions and the specific risks associated with the business. This valuation approach is considered a Level 3 fair value measurement. If actual results, market and economic conditions, including interest rates, and other factors are not consistent with management’s estimates and assumptions used in this calculation, the Company may be exposed to additional impairment losses. The CEC Combination resulted in a loss of $6.5 million, which was recorded in “Loss from formation of equity method investment” in the accompanying consolidated statements of operations for the year ended December 31, 2017. The Company incurred working capital adjustments, funding for certain post-closing commitments, and transaction fees, of which $3.3 million and $1.0 million was unpaid and recorded in “Accrued liabilities” in the accompanying consolidated balance sheets as of December 31, 2018 and 2019, respectively. Included in this loss amount is goodwill of $3.6 million that was allocated to the disposed assets based on the relative fair values of those assets and the portion of the reporting unit that was retained. Prior to the CEC Combination, CEC had a pre-tax loss of $45.1 million for fiscal year 2017. Subsequent to December 29, 2017, the Company recorded an increase of $1.2 million in anticipated relocation expenses under the investment agreement in “Accrued liabilities” in the accompanying consolidated balance sheet as of December 31, 2018 and in “Loss from formation of equity method investment” in the accompanying consolidated statements of operations for the year ended December 31, 2018. The Company recorded income (loss) from this investment of $(2.9) million and $0.0 million for the years ended December 31, 2018 and 2019, respectively. The Company had an investment balance in SAFE&CEC S.r.l. of $23.4 million and $23.7 million as of December 31, 2018 and 2019, respectively. The Company determined that the CEC Combination did not meet the definition of a discontinued operation because the disposal did not represent a strategic shift that will have a major effect on the Company’s operations and financial results.

Investments in Other Entities and Noncontrolling Interest in a Subsidiary

12 Months Ended

Dec. 31, 2019

Investments, All Other Investments [Abstract]

Investments in Other Entities and Noncontrolling Interest in a Subsidiary

Note 5 —Investments in Other Entities and Noncontrolling Interest in a Subsidiary

SAFE&CEC S.r.l.

On December 29, 2017, the Company obtained a 49% ownership interest in SAFE&CEC S.r.l. See Note 4 for more information.

Summarized financial information for SAFE&CEC S.r.l. is as follows (in thousands):


	Year Ended December 31,
	2018		2019
Revenue	$	68,373	$	80,886
Gross profit	$	20,124	$	20,525
Operating income (loss)	$	(4,881)	$	1,207
Net income (loss)	$	(5,499)	$	93


	As of December 31,
	2018		2019
Current assets	$	42,568	$	56,765
Non-current assets		48,629		56,153
Total assets	$	91,197	$	112,918

Current liabilities	$	36,177	$	51,911
Non-current liabilities		6,955		11,952
Total liabilities	$	43,132	$	63,863

MCEP

On September 16, 2014, the Company formed a joint venture with Mansfield Ventures LLC (“Mansfield Ventures”) called Mansfield Clean Energy Partners LLC (“MCEP”), which is designed to provide natural gas fueling solutions to bulk fuel haulers in the United States. The Company and Mansfield Ventures each have a 50% ownership interest in MCEP. The Company accounts for its interest in MCEP using the equity method of accounting because the Company does not control but has the ability to exercise significant influence over MCEP’s operations. The Company recorded income (loss) from this investment of $(0.1) million, $0.2 million and $(0.1) million for the years ended December 31, 2017, 2018, and 2019, respectively. The Company had an investment balance in MCEP of $1.7 million and $1.6 million as of December 31, 2018 and 2019, respectively.

NG Advantage

On October 14, 2014, the Company entered into a Common Unit Purchase Agreement (“UPA”) with NG Advantage for a 53.3% controlling interest in NG Advantage. NG Advantage is engaged in the business of transporting CNG in high-capacity trailers to industrial and institutional energy users, such as hospitals, food processors, manufacturers and paper mills that do not have direct access to natural gas pipelines.

On July 14, 2017, the Company contributed to NG Advantage all of its right, title and interest in and to a CNG fueling station located in Milton, Vermont. The Company purchased this CNG fueling station from NG Advantage in October 2014 in connection with the UPA, and at that time, the Company entered into a lease agreement with NG Advantage to lease the station back to NG Advantage. This lease agreement was terminated contemporaneously with the contribution of the station to NG Advantage in July 2017. As consideration for the contribution, NG Advantage issued to the Company Series A Preferred Units with an aggregate value of $7.5 million. The Series A Preferred Units provide for an accrued return upon a liquidation event with respect to NG Advantage and will convert into common units of NG Advantage if and when it completes a future equity financing that satisfies certain specified conditions; however, the Series A Preferred Units do not, in themselves, increase the Company’s controlling interest in NG Advantage. As a result, immediately following the contribution, the Company’s controlling interest in NG Advantage remained at 53.3%.

NG Advantage has entered into an arrangement with BP for the supply, sale and reservation of a specified volume of CNG transportation capacity until March 2022. On February 28, 2018, the Company entered into a guaranty agreement with NG Advantage and BP pursuant to which the Company guarantees NG Advantage’s payment obligations to BP in the event of default by NG Advantage under the supply arrangement, in an amount up to an aggregate of $30.0 million plus related fees. This guaranty is in effect until thirty days following the Company’s notice to BP of its termination. As initial consideration for the guaranty agreement, NG Advantage issued to the Company 19,660 common units, which increased the Company’s controlling interest in NG Advantage from 53.3% to 53.5%.

On October 1, 2018, the Company purchased 1,000,001 common units from NG Advantage for an aggregate cash purchase price of $5.0 million. This purchase increased Clean Energy’s controlling interest in NG Advantage from 53.5% to 61.7%.

In each month from November 2018 through February 2019, the Company was issued 100,000 additional common units of NG Advantage, for a total of 400,000 common units, pursuant to the guaranty agreement entered in February 2018. The issuance of 400,000 additional common units increased the Company’s controlling interest in NG Advantage to 63.0% and 64.6% as of December 31, 2018 and 2019, respectively.

On February 15, 2019, NG Advantage and the Company entered into a transaction pursuant to which the Company agreed to lend to NG Advantage up to $5.0 million in accordance with the terms of a delayed draw convertible promissory note (the “2019 Note”). NG Advantage simultaneously drew $2.5 million under the 2019 Note, and on April 15, 2019, NG Advantage drew the remaining $2.5 million under the 2019 Note. As discussed below, on June 28, 2019, all unpaid principal and accrued interest under the 2019 Note was subsumed within the 2019 Convertible Note (as defined below).

On May 17, 2019, the Company agreed to lend to NG Advantage up to $0.5 million in accordance with the terms of a promissory note (the “2019 Bridge Loan”). On June 11, 2019, NG Advantage drew $0.1 million under the 2019 Bridge Loan. As discussed below, on June 28, 2019, all unpaid principal and accrued interest under the 2019 Bridge Loan was subsumed within the 2019 Convertible Note.

On June 28, 2019, the Company agreed to lend to NG Advantage up to $15.2 million in accordance with the terms of a delayed draw convertible promissory note (the “June 2019 Convertible Note”). NG Advantage simultaneously drew $3.5 million under the June 2019 Convertible Note. The outstanding principal and accrued interest under the 2019 Note and 2019 Bridge Loan were incorporated into the June 2019 Convertible Note, which resulted in the cancellation of the 2019 Note and 2019 Bridge Loan. In connection with the June 2019 Convertible Note, NG Advantage issued to the Company a warrant to purchase 86,879 common units. During the period of July 1, 2019 through November 26, 2019, NG Advantage drew an additional $7.4 million under the June 2019 Convertible Note.

On November 27, 2019, the Company agreed to lend to NG Advantage up to $26.7 million in accordance with the terms of a delayed draw convertible promissory note (the “November 2019 Convertible Note”). NG Advantage simultaneously drew $3.4 million under the November 2019 Convertible Note. The outstanding principal and accrued interest under the June 2019 Convertible Note were incorporated into the November 2019 Convertible Note, which resulted in the cancellation of the June 2019 Convertible Note. All outstanding principal under the November 2019 Convertible Note bore interest at a rate of 12.0% per annum, and all unpaid principal and accrued interest under the November 2019 Convertible Note was due on the earlier of December 31, 2019, subject to extension at the Company's discretion, or the occurrence of an event of default (subject to notice requirements and cure periods in certain circumstances). In connection with the November 2019 Convertible Note, NG Advantage issued to the Company a warrant to purchase 2,000,000 common units. In December 2019, NG Advantage drew an additional $6.6 million under the November 2019 Convertible Note. As of December 31, 2019, NG Advantage had an outstanding balance of $26.7 million, plus accrued and unpaid interest, under the November 2019 Convertible Note. This intercompany transaction has been eliminated in consolidation. See Note 23 —Subsequent Events for additional information about the November 2019 Convertible Note.

The Company recorded a loss attributable to the noncontrolling interest in NG Advantage of $2.2 million, $5.4 million and $7.2 million for the years ended December 31, 2017, 2018, and 2019, respectively. The noncontrolling interest was $17.0 million and $9.6 million as of December 31, 2018 and 2019, respectively.

Cash, Cash Equivalents and Restricted Cash

12 Months Ended

Dec. 31, 2019

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents and Restricted Cash

Note 6 —Cash, Cash Equivalents and Restricted Cash

Cash, cash equivalents and restricted cash as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Current assets:
Cash and cash equivalents	$	29,844	$	49,207
Restricted cash - standby letters of credit		30		15
Restricted cash - held in escrow		750		—
Total cash, cash equivalents and current portion of restricted cash	$	30,624	$	49,222

Long-term assets:
Restricted cash - standby letters of credit	$	4,000	$	4,000
Total long-term portion of restricted cash	$	4,000	$	4,000

Total cash, cash equivalents and restricted cash	$	34,624	$	53,222

The Company considers all highly liquid investments with maturities of three months or less on the date of acquisition to be cash equivalents.

The Company places its cash and cash equivalents with high credit quality financial institutions. At times, such investments may be in excess of the Federal Deposit Insurance Corporation (“FDIC”) and Canadian Deposit Insurance Corporation (“CDIC”) limits. Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash deposits. The amounts in excess of FDIC and CDIC limits were approximately $28.5 million and $47.9 million as of December 31, 2018 and 2019, respectively.

The Company classifies restricted cash as short-term and a current asset if the cash is expected to be used in operations within a year or to acquire a current asset. Otherwise, the restricted cash is classified as long-term. Short-term restricted cash consisted of standby letters of credit renewed annually. Long-term restricted cash consisted of a standby letter of credit.

Short-Term Investments

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Short-Term Investments

Note 7 — Short-Term Investments

Short-term investments include available-for-sale debt securities and certificates of deposit. Available-for-sale debt securities are carried at fair value, inclusive of unrealized gains and losses. Unrealized gains and losses on available for sale debt securities are recognized in other comprehensive income (loss), net of applicable income taxes. Gains or losses on sales of available-for-sale debt securities are recognized on the specific identification basis.

The Company reviews available-for-sale debt securities for other-than-temporary declines in fair value below their cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below its cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security. As of December 31, 2019, the Company believes the carrying values for its available-for-sale debt securities are properly recorded.

Short-term investments as of December 31, 2018 consisted of the following (in thousands):


			Gross
	Amortized		Unrealized		Estimated
	Cost		Losses		Fair Value
Municipal bonds and notes	$	9,210	$	(19)	$	9,191
Zero coupon bonds		29,823		(28)		29,795
Corporate bonds		26,175		(22)		26,153
Certificates of deposit		507		—		507
Total short-term investments	$	65,715	$	(69)	$	65,646

Short-term investments as of December 31, 2019 consisted of the following (in thousands):


			Gross
	Amortized		Unrealized		Estimated
	Cost		Losses		Fair Value
Municipal bonds and notes	$	2,986	$	—	$	2,986
Zero coupon bonds		33,919		—		33,919
Corporate bonds		19,509		(3)		19,506
Certificates of deposit		518		—		518
Total short-term investments	$	56,932	$	(3)	$	56,929

Derivative Instruments and Hedging Activities

12 Months Ended

Dec. 31, 2019

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments and Hedging Activities

Note 8 - Derivative Instruments and Hedging Activities

In October 2018, the Company executed two commodity swap contracts with Total Gas & Power North America, an affiliate of TOTAL and THUSA (as defined in Notes 13 and 14), for a total of five million diesel gallons annually from April 1, 2019 to June 30, 2024. These commodity swap contracts are used to manage diesel price fluctuation risks related to the natural gas fuel supply commitments the Company makes in its fueling agreements with fleet operators that participate in the Zero Now truck financing program. These contracts are not designated as accounting hedges and as a result, changes in the fair value of these derivative instruments are recognized in "Product revenue" in the accompanying consolidated statements of operations.

During 2019, the Company entered into fueling agreements with fleet operators under the Zero Now truck financing program. The fueling agreements contain a pricing feature indexed to diesel, which the Company determined to be embedded derivatives and recorded at fair value at the time of execution, with the changes in fair value of the embedded derivatives recognized as earnings in "Product revenue" in the accompanying consolidated statements of operations.

Derivatives as of December 31, 2018 consisted of the following (in thousands):


	Gross Amounts		Gross Amounts		Net Amount
	Recognized		Offset		Presented
Assets:
Commodity swaps:
Current portion of derivative assets, related party	$	1,508	$	—	$	1,508
Long-term portion of derivative assets, related party		8,824		—		8,824
Total derivative assets	$	10,332	$	—	$	10,332

Derivatives and embedded derivatives as of as of December 31, 2019 consisted of the following (in thousands):


	Gross Amounts		Gross Amounts		Net Amount
	Recognized		Offset		Presented
Assets:
Commodity swaps:
Long-term portion of derivative assets, related party	$	3,270	$	—	$	3,270
Fueling agreements:
Prepaid expenses and other current assets		232		—		232
Notes receivable and other long-term assets, net		491		—		491
Total derivative assets	$	3,993	$	—	$	3,993
Liabilities:
Commodity swaps:
Current portion of derivative liabilities, related party	$	164	$	—	$	164
Fueling agreements:
Accrued liabilities		42		—		42
Other long-term liabilities		39		—		39
Total derivative liabilities	$	245	$	—	$	245

As of December 31, 2018 and 2019, the Company had a total volume on open commodity swap contracts of 25.0 million and 21.9 million diesel gallons at a weighted-average price per gallon of approximately $3.18 and $2.30, respectively.

The following table reflects the weighted-average price of open commodity swap contracts as of December 31, 2018 and 2019, by year with associated volumes:


	December 31, 2018			December 31, 2019
	Volumes	Weighted -Average Price per		Volumes	Weighted -average Price per
Year	(Diesel Gallons)	Diesel Gallon		(Diesel Gallons)	Diesel Gallon
2019	3,125,000	$	3.18	—	$	—
2020	5,000,000	$	3.18	4,986,000	$	2.37
2021	5,000,000	$	3.18	5,000,000	$	2.34
2022	5,000,000	$	3.18	5,000,000	$	2.34
2023	5,000,000	$	3.18	5,000,000	$	2.34
2024	1,875,000	$	3.18	1,870,000	$	1.76

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 9 —Fair Value Measurements

The Company follows the authoritative guidance for fair value measurements with respect to assets and liabilities that are measured at fair value on a recurring basis and non-recurring basis. Under the standard, fair value is defined as the exit price, or the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants, as of the measurement date. The standard also establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use in valuing the asset or liability developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would use in valuing the asset or liability developed based upon the best information available in the circumstances. The hierarchy consists of the following three levels: Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 inputs include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs (other than quoted prices) that are observable for the asset or liability, either directly or indirectly; Level 3 inputs are unobservable inputs for the asset or liability. Categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The Company’s available-for-sale debt securities and certificate of deposits are classified within Level 2 because they are valued using the most recent quoted prices for identical assets in markets that are not active and quoted prices for similar assets in active markets.

The Company used the income approach to value its outstanding commodity swap contracts and embedded derivatives in its fueling agreements under the Zero Now truck financing program (see Note 8). Under the income approach, the Company used a discounted cash flow (“DCF”) model in which cash flows anticipated over the term of the contracts are discounted to their present value using an expected discount rate. The discount rate used for cash flows reflects the specific risks in spot and forward rates and credit valuation adjustments. This valuation approach is considered a Level 3 fair value measurement. The significant unobservable inputs used in the fair value measurement of the Company’s derivative instruments are Ultra-Low Sulfur Diesel (“ULSD”) forward prices and differentials from ULSD to Petroleum Administration for Defense District (“PADD”) regions. Significant increases (decreases) in any of those inputs in isolation would result in a significantly lower (higher) fair value measurement. Generally, a change in the ULSD forward prices is accompanied by a directionally opposite but less extreme change in the ULSD-PADD differential.

The Company estimated the fair value of its outstanding commodity swap contracts based on the following inputs as of December 31, 2018 and 2019:


	December 31, 2018			December 31, 2019
Significant Unobservable Inputs	Input Range	Weighted Average		Input Range	Weighted Average
ULSD Gulf Coast Forward Curve	$1.71 - $1.79	$	1.75	$1.76 - $1.88	$	1.81
Historical Differential to PADD 3 Diesel	$0.76 - $1.16	$	0.89	$0.79 - $1.16	$	0.91
Historical Differential to PADD 5 Diesel	$1.22 - $2.12	$	1.55	$1.32 - $2.30	$	1.78

The Company estimated the fair value of embedded derivatives in its fueling agreements under the Zero Now truck financing program based on the following inputs as of December 31, 2019:


	December 31, 2019
Significant Unobservable Inputs	Input Range	Weighted Average
ULSD Gulf Coast Forward Curve	$1.76 - $1.88	$	1.81
Historical Differential to PADD 5 Diesel	$1.32 - $2.30	$	1.78

The Company’s liability-classified warrants (or "derivative warrants"), which were all issued by NG Advantage, are classified within Level 3 because the Company uses the Black-Scholes option pricing model to estimate the fair value based on inputs that are not observable in any market.

There were no transfers of assets between Level 1, Level 2, or Level 3 of the fair value hierarchy as of December 31, 2018 or 2019.

The following tables provide information by level for assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2018 and 2019 (in thousands):


	December 31, 2018		Level 1		Level 2		Level 3
Assets:
Available-for-sale securities (1):
Municipal bonds and notes	$	9,191	$	—	$	9,191	$	—
Zero coupon bonds		29,795		—		29,795		—
Corporate bonds		26,153		—		26,153		—
Certificates of deposit (1)		507		—		507		—
Commodity swap contracts (2)		10,332		—		—		10,332
Embedded derivatives (3)		—		—		—		—
Liabilities:
Warrants (4)	$	1,079	$	—	$	—	$	1,079


	December 31, 2019		Level 1		Level 2		Level 3
Assets:
Available-for-sale securities (1):
Municipal bonds and notes	$	2,986	$	—	$	2,986	$	—
Zero coupon bonds		33,919		—		33,919		—
Corporate bonds		19,506		—		19,506		—
Certificates of deposit (1)		518		—		518		—
Commodity swap contracts (2)		3,270		—		—		3,270
Embedded derivatives (3)		723		—		—		723
Liabilities:
Commodity swap contracts (2)	$	164	$	—	$	—	$	164
Embedded derivatives (3)		81		—		—		81
Warrants (4)		40		—		—		40

(1)

Included in “Short-term investments” in the accompanying consolidated balance sheets. See Note 7 for more information.

(2)

Included in “Derivative assets, related party” and “Long-term portion of derivative assets, related party” as of December 31, 2018, and “Derivative liabilities, related party” and “Long-term portion of derivative assets, related party” as of December 31, 2019, in the accompanying consolidated balance sheets. See Note 8 for more information.

(3)

Included in "Prepaid expenses and other current assets", "Notes receivable and other long-term assets, net", “Accrued liabilities” and “Other long-term liabilities” in the accompanying consolidated balance sheets. See Note 8 for more information.

(4)

Included in "Other long-term liabilities" as of December 31, 2018, and “Accrued liabilities” as of December 31, 2019 in the accompanying consolidated balance sheets.

The following table provides a reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis as shown in the tables above that used significant unobservable inputs (Level 3), as well as the change in unrealized gains or losses for the periods included in earnings (in thousands):


	Assets:		Assets:		Liabilities:		Liabilities:
	Commodity		Embedded		Commodity		Embedded		Liabilities:
	Swap Contracts		Derivatives		Swap Contracts		Derivatives		Warrants
Balance as of December 31, 2017	$	—	$	—	$	—	$	—	$	(536)
Total gain (loss)		10,332		—		—		—		(543)
Balance as of December 31, 2018	$	10,332	$	—	$	—	$	—	$	(1,079)

Balance as of December 31, 2018	$	10,332	$	—	$	—	$	—	$	(1,079)
Settlements, net		667		—		—		—		—
Total gain (loss)		(7,729)		723		(164)		(81)		1,039
Balance as of December 31, 2019	$	3,270	$	723	$	(164)	$	(81)	$	(40)

Change in unrealized gain (loss) for the year ended December 31, 2018 included in earnings	$	10,332	$	—	$	—	$	—	$	(543)
Change in unrealized gain (loss) for the year ended December 31, 2019 included in earnings	$	(7,062)	$	723	$	(164)	$	(81)	$	1,039

Other Financial Assets and Liabilities

The carrying amounts of the Company’s cash, cash equivalents and restricted cash, receivables and payables approximate fair value due to the short-term nature of those instruments. The carrying amounts of the Company’s debt instruments approximated their respective fair values as of December 31, 2018 and 2019. The fair values of these debt instruments were estimated using a discounted cash flow analysis based on interest rates offered on loans with similar terms to borrowers of similar credit quality, which are Level 3 inputs. See Note 13 for more information about the Company’s debt instruments.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Other Receivables

12 Months Ended

Dec. 31, 2019

Receivables [Abstract]

Other Receivables

Note 10 —Other Receivables

Other receivables as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Loans to customers to finance vehicle purchases	$	276	$	653
Accrued customer billings		6,261		6,124
Fuel tax credits		434		69,585
Other		8,573		8,536
Total other receivables	$	15,544	$	84,898

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Land, Property and Equipment

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Land, Property and Equipment

Note 11 —Land, Property and Equipment

Land, property and equipment, net as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Land	$	3,681	$	3,476
LNG liquefaction plants		94,633		94,633
Station equipment		319,119		324,431
Trailers		75,901		79,477
Other equipment		97,268		101,655
Construction in progress		73,485		75,232
		664,087		678,904
Less accumulated depreciation		(313,519)		(354,992)
Total land, property and equipment, net	$	350,568	$	323,912

Included in "Land, property and equipment, net" are capitalized software costs of $29.3 million and $30.4 million as of December 31, 2018 and 2019, respectively. Accumulated amortization of the capitalized software costs is $22.5 million and $26.3 million as of December 31, 2018 and 2019, respectively.

The Company recorded amortization expense related to the capitalized software costs of $4.4 million, $3.7 million and $3.9 million during the years ended December 31, 2017, 2018, and 2019, respectively.

As of December 31, 2018, and 2019, $4.6 million and $3.0 million, respectively, are included in "Accounts payable" and "Accrued liabilities" in the accompanying consolidated balance sheets which amounts are related to purchases of property and equipment. These amounts are excluded from the accompanying consolidated statements of cash flows as they are non-cash investing activities.

Accrued Liabilities

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

Accrued Liabilities

Note 12 —Accrued Liabilities

Accrued liabilities as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Accrued alternative fuels incentives (1)	$	6,923	$	27,839
Accrued employee benefits		2,248		2,276
Accrued interest		78		220
Accrued gas and equipment purchases		12,833		11,383
Accrued property and other taxes		3,397		3,732
Accrued salaries and wages		8,609		9,105
Other (2)		14,381		13,142
Total accrued liabilities	$	48,469	$	67,697

(1)

Includes the amount of RINs, LCFS Credits and the amount of AFTC payable to third parties.

(2)

The amounts as of December 31, 2018 and 2019 include lease termination fees and AROs related to the closure of certain fueling stations and working capital adjustments (see Note 3 for more information), in addition to funding for certain commitments and transaction fees incurred as a result of the CEC Combination (see Note 4 for more information). No individual item in “Other” exceeds 5% of total current liabilities.

Debt

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Debt

Note 13 —Debt

Debt obligations as of December 31, 2018 and 2019 consisted of the following (in thousands):


	December 31, 2018
			Unamortized Debt		Balance, Net of
	Principal Balances		Financing Costs		Financing Costs
7.5% Notes	$	50,000	$	58	$	49,942
NG Advantage debt		28,904		155		28,749
Other debt		1,024		—		1,024
Total debt		79,928		213		79,715
Less amounts due within one year		(4,811)		(99)		(4,712)
Total long-term debt	$	75,117	$	114	$	75,003


	December 31, 2019
			Unamortized Debt		Balance, Net of
	Principal Balances		Financing Costs		Financing Costs
7.5% Notes	$	50,000	$	17	$	49,983
NG Advantage debt		33,898		192		33,706
SG Facility		4,400		—		4,400
Other debt		796		—		796
Total debt		89,094		209		88,885
Less amounts due within one year		(56,097)		(84)		(56,013)
Total long-term debt	$	32,997	$	125	$	32,872

The following is a summary of the aggregate maturities of debt obligations for each of the yearly periods subsequent to December 31, 2019 (in thousands):


	2020		2021		2022		2023		2024		Thereafter		Total
7.5% Notes	$	50,000	$	—	$	—	$	—	$	—	$	—	$	50,000
NG Advantage debt		5,857		6,092		6,300		11,407		4,242		—		33,898
SG Facility		—		—		—		—		4,400		—		4,400
Other debt		240		248		215		93		—		—		796
Total	$	56,097	$	6,340	$	6,515	$	11,500	$	8,642	$	—	$	89,094

7.5% Notes

In June 2013, the Company issued notes (the “7.5% Notes”) to T. Boone Pickens and Green Energy Investment Holdings, LLC (“GEIH”) in the amount of $150.0 million. The 7.5% Notes bear interest at the rate of 7.5% per annum and are convertible at the option of the holder into shares of the Company’s common stock at a conversion price of $15.80 per share (the “7.5% Notes Conversion Price”). Upon written notice to the Company, each holder of a 7.5% Note has the right to exchange all or any portion of the principal and accrued and unpaid interest under its 7.5% Notes for shares of the Company’s common stock at the 7.5% Notes Conversion Price. Additionally, subject to certain restrictions, the Company can force conversion of each 7.5% Note into shares of its common stock if such shares trade at a 40% premium to the 7.5% Notes Conversion Price for at least 20 trading days in any consecutive 30 trading day period.

The entire principal balance of each 7.5% Note is due and payable seven years following its original issuance and the Company may repay each 7.5% Note at maturity in shares of its common stock (provided that the Company may not issue more than 13,993,630 shares of its common stock to holders of 7.5% Notes) or cash. All of the shares issuable upon conversion of the 7.5% Notes have been registered for resale by their holders pursuant to a registration statement that has been filed with and declared effective by the Securities and Exchange Commission.

The 7.5% Notes include customary events of default which, if any of them occurs, would permit or require the principal of, and accrued interest on, the 7.5% Notes to become, or to be declared, due and payable. No events of default under the 7.5% Notes had occurred as of December 31, 2019.

On August 27, 2013, GEIH transferred $5.0 million in principal amount of its 7.5% Notes to third parties.

On February 9, 2017, the Company purchased from Mr. Pickens his 7.5% Note due July 2018, having an outstanding principal amount of $25.0 million, for a cash purchase price of $21.8 million. Upon such purchase, the applicable 7.5% Notes were surrendered and canceled in full. The Company’s repurchase of this 7.5% Note resulted in a gain of $3.2 million for the year ended December 31, 2017.

On February 21, 2017, GEIH transferred $11.8 million in principal amount of its 7.5% Notes to third parties.

On November 17, 2017, Mr. Pickens transferred all remaining $40.0 million in principal amount of his 7.5% Notes to a third party.

On June 29, 2018, and pursuant to the consent of the holders of the 7.5% Notes to the Company’s payments of amounts owed thereunder before maturity, the Company paid to the holders, in cash, an aggregate of $25.0 million in principal amount and $0.5 million in accrued and unpaid interest owed under all outstanding 7.5% Notes due July 2018. Upon such payment, the purchased 7.5% Notes were canceled in full.

On December 4, 2018, the Company purchased from the holders, thereof all outstanding 7.5% Notes due July 2019, having an aggregate outstanding principal amount of $50.0 million, for a cash purchase price of $50.5 million. Upon such payment, the purchased 7.5% Notes were canceled in full.

As a result of the foregoing transactions, as of December 31, 2019, (i) GEIH held 7.5% Notes in an aggregate principal amount of $32.9 million and (ii) other third parties held 7.5% Notes in an aggregate principal amount of $17.1 million, all of which mature in June 2020.

Plains Credit Facility

On February 29, 2016, the Company entered into a Loan and Security Agreement (the “Plains LSA”) with Plains Capital Bank (“Plains”), which, as amended on December 6, 2017, had a maturity date of September 30, 2019. Pursuant to the Plains LSA, Plains agreed to lend the Company up to $50.0 million on a revolving basis from time to time (the “Credit Facility”). There was no activity or borrowings under this Credit Facility during the years ended December 31, 2018 and 2019, and the Credit Facility matured and was canceled on September 30, 2019.

SG Credit Agreement

On January 2, 2019, the Company entered into a term credit agreement (the “Credit Agreement”) with Société Générale, a company incorporated as a société anonyme under the laws of France (“SG”). The Credit Agreement provides for a term loan facility (the “SG Facility”) pursuant to which the Company may obtain, subject to certain conditions, up to $100.0 million of loans (“SG Loans”) in support of its Zero Now truck financing program. Under the Credit Agreement, the Company is permitted to use the proceeds from the SG Loans solely to fund the incremental cost of trucks purchased or financed under the Zero Now truck financing program and related fees and expenses incurred by the Company in connection therewith. Interest on outstanding SG Loans accrues at a rate equal to LIBOR plus 1.30% per annum, and a commitment fee on any unused portion of the SG Facility accrues at a rate equal to 0.39% per annum. Interest and commitment fees are payable quarterly. The Company is required to make mandatory prepayments under the SG Facility equal to any amounts the Company receives for complete or partial refunds of the incremental cost of trucks purchased or financed under the Zero Now program, and the Company is generally permitted to make complete or partial voluntary prepayments under the SG Facility with prior written notice to SG but without premium or penalty. The Credit Agreement includes certain representations, warranties and covenants by the Company and also provides for customary events of default which, if any of them occurs, would permit or require, among other things, the principal of and accrued interest on the Loans to become or to be declared due and payable. Events of default under the Credit Agreement include, among others, nonpayment of principal and interest when due; violation of covenants; any default by the Company (whether or not resulting in acceleration) under any other agreement for borrowed money in excess of $20.0 million; voluntary or involuntary bankruptcy; repudiation or assignment of the Guaranty by THUSA; or a change of control of the Company.

The Credit Agreement does not include financial covenants, and the Company has not provided SG with any security for its obligations under the Credit Agreement. As described below, THUSA has entered into the Guaranty to guarantee the Company’s payment obligations to SG under the Credit Agreement. As of December 31, 2019, the Company had $4.4 million outstanding on the SG Facility and no events of defaults had occurred.

TOTAL Credit Support Agreement

On January 2, 2019, the Company entered into a credit support agreement (“CSA”) with Total Holdings USA Inc. (“THUSA”), a wholly owned subsidiary of TOTAL (as defined in Note 14). Under the CSA, THUSA agreed to enter into a guaranty agreement (“Guaranty”) pursuant to which it has guaranteed the Company’s obligation to repay to SG up to $100.0 million in SG Loans and interest thereon in accordance with the Credit Agreement. In consideration for the commitments of THUSA under the CSA, the Company is required to pay THUSA a quarterly guaranty fee at a rate per quarter equal to 2.5% of the average aggregate Loan amount for the preceding calendar quarter.

Following any payment by THUSA to SG under the Guaranty, the Company would be obligated to immediately pay to THUSA the full amount of such payment plus interest on such amount at a rate equal to LIBOR plus 1.0%. In addition, the Company would be obligated to pay and reimburse THUSA for all reasonable out-of-pocket expenses it incurs in the performance of its services under the CSA, including all reasonable out-of-pocket attorneys’ fees and expenses incurred in connection with the payment to SG under the Guaranty or any enforcement or attempt to enforce any of the Company‘s obligations under the CSA. The CSA includes customary representations and warranties and affirmative and negative covenants by the Company. In addition, upon the occurrence of a “Trigger Event” and during its continuation, THUSA may, among other things: elect not to guarantee additional Loans; declare all or any portion of the outstanding amounts the Company owes THUSA under the CSA to be due and payable; and exercise all other rights it may have under applicable law. Each of the following events constitutes a Trigger Event: the Company defaults with respect to any payment obligation under the CSA; any representation or warranty made by the Company in the CSA was false, incorrect, incomplete or misleading in any material respect when made; the Company fails to observe or perform any material covenant, obligation, condition or agreement in the CSA; or the Company defaults in the observance or performance of any agreement, term or condition contained in any other agreement with THUSA or an affiliate of THUSA.

As security for the Company’s obligations under the CSA, on January 2, 2019, the Company entered into a pledge and security agreement with THUSA and delivered a collateral assignment of contracts to THUSA, pursuant to which the Company collaterally assigned to THUSA all fueling agreements it enters into with participants in the Zero Now truck financing program. In addition, on January 2, 2019, the Company entered into a lockbox agreement with THUSA and Plains, under which the Company granted THUSA a security interest in the cash flow generated by the fueling agreements the Company enters into with participants in the Zero Now truck financing program.

Until the occurrence of a Trigger Event or Fundamental Trigger Event (as described below) under the CSA, the Company has the freedom to operate in the normal course and there are no restrictions on the flow of funds in and out of the lockbox account established pursuant to the lockbox agreement. Upon the occurrence of a Trigger Event under the CSA, all funds in the lockbox account will be: first, used to make scheduled debt repayments under the Credit Agreement; and second, released to the Company. Further, upon the occurrence of a “Fundamental Trigger Event” under the CSA and during its continuation, in addition to exercising any of the remedies available to THUSA upon the occurrence of a Trigger Event as described above: all participants in the Zero Now program would pay amounts owed under their fueling agreements with the Company directly into the lockbox account; under a “sweep” mechanism, all cash in the lockbox account would be used to prepay all outstanding Loans under the Credit Agreement; no other disbursements from the lockbox account could be made without THUSA’s consent; and THUSA would retain dominion over the lockbox account and the funds in the account would remain as security for the Company’s payment and reimbursement obligations under the CSA. Each of the following events constitutes a Fundamental Trigger Event: the Company defaults in the observance or performance of any agreement, term or condition contained in the Credit Agreement that would constitute an event of default thereunder, up to or beyond any grace period provided in such agreement, unless waived by SG; the Company defaults in the observance or performance of any agreement, term or condition contained in any evidence of indebtedness other than the Credit Agreement, and the effect of such default is to cause, or permit the holders of such indebtedness to cause, acceleration of indebtedness in an aggregate amount for all such collective defaults of $20.0 million or more; voluntary and involuntary bankruptcy and insolvency events; and the occurrence of a change of control of the Company.

The CSA will terminate following the later of: the payment in full of all of the Company’s obligations under the CSA; and the termination or expiration of the Guaranty following the maturity date of the last outstanding Loan or December 31, 2023, whichever is earlier.

NG Advantage Debt

On May 12, 2016 and January 24, 2017, respectively, NG Advantage entered into a Loan and Security Agreement (the “Commerce LSA”) with Commerce Bank & Trust Company (“Commerce”), pursuant to which Commerce agreed to lend NG Advantage $6.3 million and $6.2 million, respectively. The proceeds were primarily used to fund the purchases of CNG trailers and equipment. Interest and principal for both loans are payable monthly in 84 equal monthly installments at an annual rate of 4.41% and 5.0%, respectively. As collateral security for the prompt payment in full when due of NG Advantage’s obligations to Commerce under the Commerce LSA, NG Advantage pledged to and granted Commerce a security interest in all of its right, title and interest in the CNG trailers and equipment purchased with the proceeds received under the Commerce LSA.

On November 30, 2016, NG Advantage entered into a Loan and Security Agreement (the “Wintrust LSA”) with Wintrust Commercial Finance (“Wintrust”), pursuant to which Wintrust agreed to lend NG Advantage $4.7 million. The proceeds were primarily used to fund the purchases of CNG trailers and equipment. Interest and principal is payable monthly in 72 equal monthly installments at an annual rate of 5.17%. As collateral security for the prompt payment in full when due of NG Advantage’s obligations to Wintrust under the Wintrust LSA, NG Advantage pledged to and granted Wintrust a security interest in all of its right, title and interest in the CNG trailers and equipment purchased with the proceeds received under the Wintrust LSA.

Financing Obligations

NG Advantage has entered into sale and leaseback transactions with various lessors as described below. In each instance, the sale and leaseback transaction does not qualify for sale-leaseback accounting because of NG Advantage’s continuing involvement with the buyer-lessor due to a fixed price repurchase option. As a result, the transactions are recorded under the financing method, in which the assets remain on the accompanying consolidated balance sheets and the proceeds from the transactions are recorded as financing liabilities.

On December 18, 2017, NG Advantage entered into a sale-leaseback arrangement through a Master Lease Agreement (the “BoA MLA”) with Bank of America Leasing & Capital, LLC (“BoA”). Pursuant to the BoA MLA, NG Advantage received $2.1 million in cash for CNG trailers and simultaneously leased them back from BoA for five years commencing January 1, 2018 with interest and principal payable in 60 equal monthly installments at an annual rate of 4.86%.

On March 1, 2018, NG Advantage entered into a sale-leaseback arrangement through a Master Lease Agreement (the “First National MLA”) with First National Capital, LLC (“First National”). Pursuant to the First National MLA, NG Advantage received $6.3 million in cash, net of fees and the first month’s lease payment for CNG trailers and simultaneously leased them back from First National for six years commencing March 1, 2018 with interest and principal payable in 72 equal monthly installments at an annual rate of 9.28%.

On December 20, 2018 (the “Closing Date”), NG Advantage entered into a purchase agreement to sell a compression station for a purchase price of $7.0 million to an entity whose member owners were noncontrolling interest member owners of NG Advantage. On the Closing Date and immediately following the consummation of the sale of the compression station, NG Advantage entered into a lease agreement with the buyer of the station (the “Lease”) pursuant to which the station was leased back to NG Advantage for a term of five years with monthly rent payments equal to $0.1 million at an annual rate of 12.0%. Of the purchase price, NG Advantage received $4.7 million in cash, net of fees, the first month’s lease payment, and the repayment of a $2.0 million promissory note from one of the member owners of the buyer, which was issued on November 19, 2018.

On January 17, 2019, NG Advantage entered into a sale-leaseback arrangement through a Master Lease Agreement (the “Nations MLA”) with Nations Fund I, LLC (“Nations”). Pursuant to the Nations MLA, NG Advantage received $3.4 million in cash, net of the first month’s lease payment, for CNG trailers and simultaneously leased them back from Nations for four years commencing February 1, 2019 with interest and principal payable in 48 equal monthly installments at an annual rate of 9.18%.

In October 2019, NG Advantage entered into a sale-leaseback agreement, pursuant to which it sold compression equipment for a purchase price of $7.5 million and simultaneously leased it back for a term of five years with interest and principal payable in equal monthly installments at an annual rate of 10.47%. Of the purchase price, NG Advantage received $5.3 million in cash and $2.2 million is held as a security deposit.

Other Debt

The Company has other debt due at various dates through 2023 bearing interest at rates up to 5.02% and with a weighted-average interest rate of 4.78% as of December 31, 2018 and 2019.

Stockholders' Equity

12 Months Ended

Dec. 31, 2019

Stockholders' Equity Note [Abstract]

Stockholders' Equity

Note 14 —Stockholders’ Equity

Authorized Shares

The Company’s certificate of incorporation authorizes the issuance of two classes of capital stock designated as common stock and preferred stock, each having $0.0001 par value per share. As of December 31, 2019, the Company was authorized to issue 305,000,000 shares, of which 304,000,000 shares are designated common stock and 1,000,000 shares are designated preferred stock.

Dividend Provisions

The Company did not declare or pay any dividends during the years ended December 31, 2017, 2018 or 2019.

Voting Rights

Each holder of common stock has the right to one vote per share owned on matters presented for stockholder action.

Issuance of Common Stock

At-The-Market Offering Program

On May 31, 2017, the Company terminated its equity distribution agreement (the “Sales Agreement”) with Citigroup Global Markets Inc. (“Citigroup”), as sales agent and/or principal. The Sales Agreement was terminable at will upon written notification by the Company with no penalty. Pursuant to the Sales Agreement, the Company was entitled to issue and sell, from time to time through or to Citigroup, shares of its common stock having an aggregate offering price of up to $200.0 million in an “at-the-market” offering program (the “ATM Program”). The ATM Program commenced on November 11, 2015 when the Company and Citigroup entered into the original equity distribution agreement, which was amended and restated on September 9, 2016 and again on December 21, 2016 prior to its termination.

The following table summarizes the activity under the ATM Program for the periods presented:


	Year ended December 31,
(in 000s, except share amounts)	2017
Gross proceeds	$	10,767
Fees and issuance costs		311
Net proceeds	$	10,456
Shares issued		3,802,500

Total Private Placement

On May 9, 2018, the Company entered into a stock purchase agreement (the “Purchase Agreement”) with Total Marketing Services, S.A. (“Total”), a wholly owned subsidiary of TOTAL S.A. (“TOTAL”). Pursuant to the Purchase Agreement, the Company agreed to sell and issue, and Total agreed to purchase, up to 50,856,296 shares of the Company’s common stock at a purchase price of $1.64 per share, all in a private placement (the “Total Private Placement”). The purchase price per share was determined based on the volume-weighted average price for the Company’s common stock between March 23, 2018 (the day on which discussions began between the Company and Total) and May 3, 2018 (the day on which the Company agreed in principle with Total regarding the structure and basic terms of its investment). As of the date of the Purchase Agreement, Total did not hold or otherwise beneficially own any shares of the Company’s common stock, and Total has agreed, until the later of May 9, 2020 or such date when it ceases to hold more than 5.0% of the Company’s common stock then outstanding, among other similar undertakings and subject to customary conditions and exceptions, to not purchase shares of the Company’s common stock or otherwise pursue transactions that would result in Total beneficially owning more than 30.0% of the Company’s equity securities without the approval of the Company’s board of directors.

On June 13, 2018, the Company and Total closed the Total Private Placement, in which: (1) the Company issued to Total all of the 50,856,296 shares of its common stock issuable under the Purchase Agreement, resulting in Total holding approximately 25.0% of the outstanding shares of the Company’s common stock and the largest ownership position of the Company as of September 30, 2018; (2) Total paid to the Company an aggregate of $83.4 million in gross proceeds, which the Company has used and expects to continue to use for working capital and general corporate purposes, which may include executing its business plans, pursuing opportunities for further growth, and retiring a portion of its outstanding indebtedness; and (3) the Company and Total entered into a registration rights agreement, described below. In connection with the issuance of common stock, the Company incurred transaction fees of $1.9 million.

Pursuant to the Purchase Agreement, the Company and Total also entered into a registration rights agreement on June 13, 2018, upon the closing under the Purchase Agreement. Pursuant to the registration rights agreement, the Company filed a registration statement with the SEC to cover the resale of the shares issued and sold under the Purchase Agreement, which was declared effective on August 16, 2018, and is obligated to use its commercially reasonable efforts to maintain the effectiveness of such registration statement until all such shares are sold or may be sold without restriction under Rule 144 under the Securities Act of 1933, as amended. As of December 31, 2019, the Company was in compliance with all of its registration covenants set forth in the registration rights agreement.

Other

As of December 31, 2019, a third-party and a related party held outstanding warrants, which expire in 2020 and 2025, respectively, to purchase equity interests in NG Advantage. Such warrants allow the purchase of up to 765,106 NG Advantage common units and are accounted for as liability-classified warrants. The fair value was $1.1 million and $0.0 million as of December 31, 2018 and 2019, respectively (see Note 9 for more information) and the gain (loss) from the change in fair value was $0.0 million, $(0.5) million and $1.0 million for the years ended December 31, 2017, 2018, and 2019, respectively.

Stock-Based Compensation

The following table summarizes the compensation expense and related income tax benefit related to the Company’s stock-based compensation arrangements recognized in the accompanying consolidated statements of operations during the periods presented (in thousands):


	Year Ended December 31,
	2017		2018		2019
Stock-based compensation expense, net of $0 tax in 2017, 2018 and 2019 (1)	$	8,423	$	5,307	$	3,880

(1)

$0.3 million of stock-based compensation expense for the year ended December 31, 2017 is recorded in “Asset impairments and other charges” in the accompanying consolidated statements of operations and in “Asset impairments and other charges” in the accompanying consolidated statements of cash flows. See Note 3 for more information.

Equity Incentive Plans

In December 2002, the Company adopted its 2002 Stock Option Plan (“2002 Plan”).

In December 2006, the Company adopted its 2006 Equity Incentive Plan (“2006 Plan”), which became effective on May 24, 2007, the date the Company completed its initial public offering of common stock. The 2002 Plan became unavailable for new awards upon the effectiveness of the 2006 Plan, at which time unissued awards under the 2002 Plan became available for grant under the 2006 Plan.

In May 2016, the Company adopted its 2016 Performance Incentive Plan (“2016 Plan”), which became effective on May 26, 2016, the date of approval of the 2016 Plan by the Company’s stockholders. The 2006 Plan became unavailable for new awards upon the effectiveness of the 2016 Plan. Unissued awards under the 2002 and 2006 Plans are not available for future grant under the 2016 Plan. If any outstanding award under the 2002 Plan or 2006 Plan expires or is canceled, the shares allocable to the unexercised portion of that award will be added to the share reserve under the 2016 Plan and will be available for grant under the 2016 Plan. As of December 31, 2019, the Company had 2,054,993 shares available for future grant under the 2016 Plan.

Stock Options

The Company has granted stock options to key employees that vest annually over the three years following the date of grant at a rate of 34%, 33% and 33%, respectively, if the holder is in service to the Company at each vesting date. The stock options granted have contractual terms of 10 years. The stock options are subject to the terms and conditions of the 2006 and 2016 Plans and a Notice of Grant of Stock Option and Stock Option Agreement.

The following table summarizes the Company’s stock option activity for the year ended December 31, 2019:


				Weighted
				Average
		Weighted		Remaining	Aggregate
		Average		Contractual	Intrinsic
	Number of	Exercise		Term	Value
	Shares	Price		(in years)	(in thousands)
Options outstanding as of December 31, 2018	8,699,677	$	8.06
Granted	2,183,691		2.19
Exercised	(58,602)		1.79
Forfeited or expired	(1,703,101)		10.07
Options outstanding as of December 31, 2019	9,121,665	$	6.32	5.82	$	1,909
Options exercisable as of December 31, 2019	6,246,982	$	8.31	4.52	$	812
Options vested and expected to vest as of December 31, 2019	9,121,665	$	6.32	5.82	$	1,909

As of December 31, 2019, there was $1.9 million of total unrecognized compensation cost related to unvested shares underlying outstanding stock options. That cost is expected to be expensed over a remaining weighted average period of 1.45 years. The total fair value of shares vested during the year ended December 31, 2019 was $1.6 million.

The fair value of each stock option granted was estimated as of the date of grant using the Black-Scholes option pricing model and using the following assumptions:


	Year Ended December 31,
	2017	2018	2019
Dividend yield	0.0%	0.0%	0.0%
Expected volatility	63.61%	70.2% to 74.6%	57.3% to 61.5%
Risk-free interest rate	2.05%	2.70% to 2.71%	2.11% to 2.53%
Expected life in years	6.0	6.0	6.0

The volatility amounts used were estimated based on the Company’s historical and implied volatility of its traded options. The expected lives used were based on historical exercise periods and the Company’s anticipated exercise periods for its outstanding stock options. The risk-free interest rates used were based on the U.S. Treasury yield curve for the expected life of the stock options at the time of grant.

The weighted-average grant date fair values per share of stock options granted during the years ended December 31, 2017, 2018, and 2019, were $1.67, $0.88 and $1.28, respectively. The aggregate intrinsic value of options exercised during the years ended December 31, 2018 and 2019 were $0.0 million and $0.1 million, respectively. There were no options exercised during the year ended December 31, 2017. The Company recorded $2.2 million, $2.0 million and $2.2 million of stock option expense during the years ended December 31, 2017, 2018, and 2019, respectively. The Company has not recorded any tax benefit related to its stock option expense.

Service-Based Restricted Stock Units

The Company has granted service-based restricted stock units (“Service-Based RSUs”) to key employees that vest annually over the three years following the date of grant at a rate of 34%, 33% and 33%, respectively, if the holder is in service to the Company at each vesting date. The Service-Based RSUs are subject to the terms and conditions of the 2006 and 2016 Plans and a Notice of Grant of Restricted Stock Unit and Restricted Stock Unit Agreement.

The following table summarizes the Company’s Service-Based RSU activity for the year ended December 31, 2019:



		Weighted
		Average
	Number of	Fair Value at
	Shares	Grant Date
RSU outstanding as of December 31, 2018	2,279,601	$	1.88
Granted	—		—
Vested	(952,032)		2.13
Forfeited or expired	(95,764)		1.59
RSU outstanding and unvested as of December 31, 2019	1,231,805	$	1.71

The weighted average grant-date fair value of RSUs granted during the years ended December 31, 2017 and 2018 was $1.36. There were no RSUs granted during the year ended December 31, 2019.

As of December 31, 2019, there was $0.8 million of total unrecognized compensation cost related to unvested shares underlying outstanding Service-Based RSUs. That cost is expected to be expensed over a remaining weighted-average period of 0.91 years.

The Company recorded $5.9 million, $3.0 million and $1.5 million of expense during the years ended December 31, 2017, 2018, and 2019, respectively, related to the Service-Based RSUs. The Company has not recorded any tax benefit related to its Service-Based RSU expense.

Employee Stock Purchase Plan

On May 7, 2013, the Company adopted an employee stock purchase plan (the “ESPP”), pursuant to which eligible employees may purchase shares of the Company’s common stock at 85% of the fair market value of the common stock on the last trading day of two consecutive, non-concurrent offering periods each year. The Company has reserved 2,500,000 shares of its common stock for issuance under the ESPP, and the first offering period under the ESPP commenced on September 1, 2013.

The Company recorded $0.0 million of expense related to the ESPP during each of the years ended December 31, 2017, 2018, and 2019. The Company has not recorded any tax benefit related to its ESPP expense. As of December 31, 2019, the Company had issued an aggregate of 526,307 shares pursuant to the ESPP.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

Note 15 —Income Taxes

The components of income (loss) before income taxes for the years ended December 31, 2017, 2018, and 2019 are as follows (in thousands):


	2017		2018		2019
U.S.	$	(44,535)	$	(9,153)	$	14,981
Foreign		(38,770)		311		(864)
Total income (loss) before income taxes	$	(83,305)	$	(8,842)	$	14,117

The provision for income taxes for the years ended December 31, 2017, 2018, and 2019 consists of the following (in thousands):


	2017		2018		2019
Current:
Federal	$	31	$	—	$	—
State		231		341		116
Foreign		224		—		4
Total current		486		341		120
Deferred:
Federal		(978)		—		293
State		(184)		—		445
Foreign		(1,238)		—		—
Total deferred		(2,400)		—		738
Total expense (benefit)	$	(1,914)	$	341	$	858

The Company’s federal and state tax benefit from the utilization of net operating loss carryovers for the year ended December 31, 2017 was $6.9 million and $1.5 million, respectively. Income tax expense (benefit) for the years ended December 31, 2017, 2018, and 2019 differs from the “expected” amount computed using the federal income tax rate of 35% as of December 31, 2017 and 21% as of December 31, 2018 and 2019 as a result of the following (in thousands):


	2017		2018		2019
Computed expected tax (benefit)	$	(29,157)	$	(1,857)	$	2,964
Nondeductible expenses		13,420		5,674		3,087
Tax rate differential on foreign earnings		11,860		(56)		245
Joint ventures		—		947		(369)
Noncontrolling interest		—		1,133		4,114
Impact of federal income tax rate change		59,729		—		—
Tax credits		(27)		(6,603)		(10,314)
Other		2,376		985		665
Change in valuation allowance		(60,115)		118		466
Total tax expense (benefit)	$	(1,914)	$	341	$	858

On December 21, 2017, the TCJA was enacted. Among other things, the TCJA reduces the U.S. federal corporate tax rate from 35 percent to 21 percent beginning on January 1, 2018, requires companies to pay a one-time transition tax on certain previously unremitted earnings of non-U.S. subsidiaries, creates new taxes on certain foreign sourced earnings and imposes additional limitations on certain deductions, including interest expense and net operating losses arising after 2017. The Company has assessed the impact of the TCJA and is not subject to the one-time transition tax. The Company remeasured certain deferred tax assets and liabilities and uncertain tax positions based on the rates at which they are expected to reverse in the future, which is generally 21 percent under the TCJA. The decrease in the Company’s net deferred tax assets as of December 31, 2017 was offset by a corresponding decrease in its valuation allowance.

The AFTC, which had previously expired on December 31, 2016, was reinstated on February 9, 2018 to apply to vehicle fuel sales made from January 1, 2017 through December 31, 2017. As a result, all AFTC revenue for vehicle fuel the Company sold in the 2017 calendar year was recognized and collected during the year ended December 31, 2018. On December 20, 2019, AFTC was retroactively extended beginning January 1, 2018 through December 31, 2020. As a result, all AFTC revenue for vehicle fuel the Company sold in the 2018 and 2019 calendar year was recognized during the year ended December 31, 2019.

The Company recorded a federal tax benefit of $0.0 million, $6.1 million and $10.5 million related to the exclusion of AFTC associated with 2017, 2018 and 2019 fuel sales in excess of its fuel tax obligation, respectively. These amounts increased the Company’s deferred tax asset attributed to its federal net operating loss carryforwards and the Company’s deferred tax asset valuation allowance.

Deferred tax assets and liabilities result from differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities. The tax effect of temporary differences that give rise to deferred tax assets and liabilities as of December 31, 2018 and 2019 are as follows (in thousands):


	2018		2019
Deferred tax assets:
Accrued expenses	$	5,254	$	4,899
Alternative minimum tax and general business credits		6,801		6,651
Stock option expense		11,210		9,254
Other		1,998		1,456
Loss carryforwards		106,957		107,722
Total deferred tax assets		132,220		129,982
Less valuation allowance		(120,801)		(122,147)
Net deferred tax assets		11,419		7,835
Deferred tax liabilities:
Commodity swap contracts		(2,751)		(998)
Depreciation and amortization		(2,672)		(911)
Goodwill		(1,650)		(1,910)
Investments in joint ventures and partnerships		(4,346)		(4,754)
Total deferred tax liabilities		(11,419)		(8,573)
Net deferred tax liabilities	$	—	$	(738)

As of December 31, 2019, the Company had federal, state and foreign net operating loss carryforwards of approximately $430.2 million, $298.3 million and $2.0 million, respectively. The Company’s federal, state and foreign net operating loss carryforwards will, if not utilized, expire beginning in 2026, 2020 and 2030, respectively. The Company also has federal tax credit carryforwards of $6.4 million that will expire beginning in 2026. Due to the change of ownership provisions of Internal Revenue Code Section 382, utilization of a portion of the Company’s net operating loss and tax credit carryforwards may be limited in future periods.

In assessing the realizability of the net deferred tax assets, management considers whether it is more likely than not that some or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers projected future taxable income and tax planning strategies in making this assessment. As of December 31, 2018 and 2019, the Company provided a valuation allowance of $120.8 million, and $122.1 million, respectively, to reduce the net deferred tax assets due to uncertainty surrounding the realizability of these assets. The decrease in the valuation allowance for the year ended December 31, 2018 of $0.0 million was primarily attributable to the valuation allowance offsetting foreign income, partially offset by an increase in federal losses without benefit. The increase in the valuation allowance for the year ended December 31, 2019 of $1.3 million was primarily attributable to an increase in federal losses without benefit.

For the year ended December 31, 2019, the Company did not have any offshore earnings of certain non-U.S. subsidiaries which are permanently reinvested outside the United States.

The Company does not recognize the impact of a tax position in its financial statements unless the position is more likely than not to be sustained, based on the technical merits of the position. The Company has unrecognized tax benefits of $41.5 million as of December 31, 2019 that, if recognized, would not result in a tax benefit since it would be fully offset with a valuation allowance.

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits for the years ended December 31, 2017, 2018, and 2019 (in thousands):


Unrecognized tax benefit—December 31, 2017	$	34,065
Gross increases—tax positions in current year		2,178
Unrecognized tax benefit—December 31, 2018		36,243
Gross increases—tax positions in current year		5,232
Unrecognized tax benefit—December 31, 2019	$	41,475

The increase in the Company’s unrecognized tax benefits in the years ended December 31, 2018 and 2019 is primarily attributable to the portion of AFTC offset by the fuel tax the Company collected from its customers.

ASC 740, Income Taxes, requires the Company to accrue interest and penalties where there is an underpayment of taxes based on the Company’s best estimate of the amount ultimately to be paid. The Company’s policy is to recognize interest accrued related to unrecognized tax benefits and penalties as income tax expense. In addition to the unrecognized tax benefits noted above, the Company accrued $0.0 million of interest expense as of December 31, 2018 and 2019. The Company recognized interest expense related to uncertain tax positions of $0.1 million, $0.0 million and $0.0 million for the years ended December 31, 2017, 2018, and 2019, respectively.

During the year ended December 31, 2018, the IRS concluded its examination of the Company’s U.S. federal income tax returns for the year ended December 31, 2015 and did not propose any significant adjustments to the Company’s tax positions.

The Company is subject to taxation in the United States and various states and foreign jurisdictions. The Company’s tax years for 2015 through 2019 are subject to examination by various tax authorities. While the Company is no longer subject to U.S. examination for years before 2016, and for state tax examinations for years before 2015, taxing authorities can adjust the net operating losses that arose in earlier years if and when the net operating losses reduce future income. In addition, the Company is required to indemnify SAFE&CEC S.r.l. for taxes that are imposed on CEC for pre-contribution tax periods.

A number of years may elapse before an uncertain tax position is finally resolved. It is often difficult to predict the final outcome or the timing of resolution of an uncertain tax position, but the Company believes that its reserves for income taxes reflect the most probable outcomes. The Company adjusts the reserve, as well as the related interest and penalties, in light of changing facts and circumstances. The amount of penalties accrued is immaterial. Settlement of any particular position would usually require the use of cash and result in the reduction of the related reserve, or there could be a change in the amount of the Company’s net operating loss. The resolution of a matter would be recognized as an adjustment to the provision for income taxes at the effective tax rate in the period of resolution. The Company does not expect a significant increase or decrease in its uncertain tax positions within the next twelve months.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 16 —Commitments and Contingencies Environmental Matters The Company is subject to federal, state, local and foreign environmental laws and regulations. The Company does not anticipate any expenditures to comply with such laws and regulations that would have a material impact on the Company’s consolidated financial position, results of operations or liquidity. The Company believes that its operations comply, in all material respects, with applicable federal, state, local and foreign environmental laws and regulations. Litigation, Claims and Contingencies The Company may become party to various legal actions that arise in the ordinary course of its business. The Company is also subject to audit by tax and other authorities for varying periods in various federal, state, local and foreign jurisdictions, and disputes may arise during the course of these audits. It is impossible to determine the ultimate liabilities that the Company may incur resulting from any of these lawsuits, claims, proceedings, audits, commitments, contingencies and related matters or the timing of these liabilities, if any. If these matters were to ultimately be resolved unfavorably, it is possible that such an outcome could have a material adverse effect upon the Company’s consolidated financial position, results of operations, or liquidity. The Company does not, however, anticipate such an outcome and it believes the ultimate resolution of these matters will not have a material adverse effect on the Company’s consolidated financial position, results of operations, or liquidity. Long-Term Take-or-Pay Natural Gas Purchase Contracts The Company has entered into two long-term CNG supply contracts to purchase CNG, on a take-or-pay basis, expiring in December 2020 and June 2022, respectively. As of December 31, 2019, the fixed commitments under these contracts totaled approximately $0.7 million, $0.2 million, and $0.1 million for the years ending December 31, 2020, 2021 and 2022, respectively. The Company has entered into quarterly fixed price natural gas purchase contracts with take-or-pay commitments extending through June 2023. As of December 31, 2019, the fixed commitments under these contracts totaled approximately $5.0 million, $1.2 million, $1.2 million, and $1.2 million for the years ending December 31, 2020, 2021, 2022, and 2023, respectively. Long-Term Natural Gas Supply Contract In June 2017, the Company’s subsidiary, NG Advantage, entered into an arrangement with BP for the supply, sale and transportation of CNG over a five -year period starting in December 2018 and expiring March 2022. The arrangement is customary and ordinary course and provides for the payment by the customer of a nonrefundable amount of $13.4 million to reserve a specified volume of CNG transportation capacity under the arrangement, which was collected during the year ended December 31, 2017. As of December 31, 2019, the commitments for the specified volume under this contract were estimated to be approximately $5.1 million, $12.5 million, and $11.1 million for the years ending December 31, 2020, 2021 and 2022, respectively.

Leases

12 Months Ended

Dec. 31, 2019

Leases

Leases

Note 17 —Leases

New Lease Accounting Standard (Topic 842)

On January 1, 2019, the Company adopted the new lease accounting standard (see Note 1 for more information on the standard and the effect of the adoption) whereby leases are now classified as either operating leases or finance leases. The Company’s operating leases are comprised of real estate for fueling stations, office spaces, warehouses, a LNG liquefaction plant, and office equipment, and its finance leases are comprised of vehicles.

At the inception of a contract the Company assesses whether the contract is, or contains, a lease. The Company’s assessment is based on: (1) whether the contract involves the use of a distinct identified asset, (2) whether the Company obtains the right to substantially all the economic benefit from the use of the asset throughout the period, and (3) whether the Company has the right to direct the use of the asset. The commencement date of the contract is the date the lessor makes the underlying asset available for use by the lessee.

Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset during the lease term and lease liabilities represent obligations to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the commencement date based on the net present value of fixed lease payments over the lease term. ROU assets also include any initial direct costs and advance lease payments made and exclude lease incentives. Lease liabilities also include terminal purchase options when deemed reasonably certain to exercise. The Company’s lease term includes options to extend when it is reasonably certain that it will exercise that option. The Company has elected not to recognize ROU assets and lease liabilities for short-term leases that have a term of 12 months or less; the Company recognizes lease expense for these leases on a straight-line basis over the lease term.

As most of the Company’s operating leases do not have an implicit rate that can be readily determined, the Company uses its secured incremental borrowing rate for the same term as the underlying lease based on information available at lease commencement. For finance leases, the Company uses the rate implicit in the lease.

The lease classification affects the expense recognition on the consolidated statements of operations. Operating lease charges are recorded in “Cost of sales, exclusive of depreciation and amortization,” and “Selling, general and administrative” expense. Finance lease charges are split, whereby depreciation on assets under finance leases is recorded in “Depreciation and amortization” expense and an implied interest component is recorded in “Interest expense.” The expense recognition for operating leases and finance leases is substantially consistent with legacy accounting.

The Company leased office space from the estate of T. Boone Pickens in Dallas, Texas. The Company incurred rent expense of $0.1 million in each of the years ended December 31, 2017, 2018 and 2019. The lease expired in October 2019.

NG Advantage has provided residual value guarantees on leases of certain vehicles aggregating $1.4 million to the lessors. NG Advantage expects to owe these amounts in full and therefore they have been included in the measurement of the lease liabilities and ROU assets.

Certain of the Company’s real estate leases contain variable lease payments, including payments based on a change in the index or gasoline gallon equivalents of natural gas dispensed at fueling stations. These variable lease payments cannot be determined at the commencement of the lease, are not included in the ROU assets and lease liabilities, and are recorded as a period expense when incurred.

Lessee Accounting

As of December 31, 2019, the Company’s finance and operating lease asset and liability balances were as follows (in thousands):


	2019
Finance leases:
Land, property and equipment, gross	$	5,177
Accumulated depreciation		(2,134)
Land, property and equipment, net	$	3,043

Current portion of finance lease obligations	$	615
Long-term portion of finance lease obligations		2,715
Total finance lease liabilities	$	3,330

Operating leases:
Operating lease right-of-use assets (1)	$	28,627

Current portion of operating lease obligations	$	3,359
Long-term portion of operating lease obligations		26,206
Total operating lease liabilities	$	29,565

The Company’s operating lease ROU assets are comprised of the following (in thousands):


	December 31, 2019
	Assets		Liabilities
Real estate for fueling stations	$	17,978	$	17,978
LNG plant, office spaces and warehouses		10,624		11,562
Office equipment		25		25
Total operating lease right-of-use assets	$	28,627	$	29,565

The components of lease expense for finance and operating leases consisted of the following (in thousands):


	Year Ended
	December 31, 2019
Finance leases:
Depreciation on assets under finance leases	$	498
Interest on lease liabilities		189
Total finance leases expense	$	687

Operating leases:
Lease expense	$	6,630
Lease expense on short-term leases		1,950
Variable lease expense		2,755
Sublease income		(206)
Total operating leases expense	$	11,129

Supplemental information on finance and operating leases is as follows (dollars in thousands):


	Year Ended
	December 31, 2019
Operating cash outflows from finance leases	$	189
Operating cash outflows from operating leases	$	5,350
Financing cash outflows from finance leases	$	1,667

Assets obtained in exchange for new finance lease liabilities (1)	$	519
ROU assets obtained in exchange for operating lease liabilities (1)	$	31,861


		December 31, 2019
Weighted-average remaining lease term - finance leases		4.49 years
Weighted-average remaining lease term - operating leases		11.10 years

Weighted-average discount rate - finance leases		5.09%
Weighted-average discount rate - operating leases		8.29%

(1)

These amounts are excluded from the accompanying consolidated statements of cash flows as they are non-cash investing and financing activities.

The following schedule represents the Company’s maturities of finance and operating lease liabilities as of December 31, 2019 (in thousands):


	Finance Leases		Operating Leases
Fiscal year:
2020	$	767	$	5,484
2021		679		4,658
2022		560		3,736
2023		462		3,712
2024		1,026		3,704
Thereafter		314		25,208
Total minimum lease payments		3,808		46,502
Less amount representing interest		(478)		(16,937)
Present value of lease liabilities	$	3,330	$	29,565

Lessor Accounting

The Company leases fueling station equipment to customers that contain an option to extend and an end-of-term purchase option. Receivables from these leases are accounted for as finance leases, specifically sales-type leases, and are included in “Other receivables” and “Notes receivable and other long-term assets, net” in the accompanying consolidated balance sheets.

The Company recognizes the net investment in the lease as the sum of the lease receivable and the unguaranteed residual value, both of which are measured at the present value using the interest rate implicit in the lease.

During the year ended December 31, 2019, the Company recognized $0.1 million in “Interest income” on its lease receivables.

The following schedule represents the Company’s maturities of lease receivables as of December 31, 2019 (in thousands):


Fiscal year:
2020	$	186
2021		186
2022		186
2023		186
2024		186
Thereafter		1,054
Total minimum lease payments		1,984
Less amount representing interest		(935)
Present value of lease receivables	$	1,049

Legacy Lease Disclosures (Topic 840)

As required by the new lease accounting standard, certain legacy lease disclosures are provided below as of December 31, 2018, prior to adoption of the new standard.

Operating Lease Commitments

The Company leases facilities, including the land for its LNG production plant in Boron, California and certain equipment under noncancelable operating leases expiring at various dates through 2038. If a lease has a fixed and determinable escalation clause, or periods of rent holidays, the difference between rental expense and rent paid is included in “Accrued liabilities” and “Other long-term liabilities” in the accompanying condensed consolidated balance sheets.

The following schedule represents the Company’s future minimum lease obligations under all noncancelable operating leases as of December 31, 2018 (in thousands):


Fiscal year:
2019	$	6,340
2020		4,332
2021		3,311
2022		2,409
2023		2,300
Thereafter		13,214
Total future minimum lease payments	$	31,906

Rent expense totaled $6.6 million for the year ended December 31, 2018.

Capital Lease Obligations and Receivables

The Company leases equipment under capital leases with a weighted-average interest rate of 4.48%. As of December 31, 2018, future payments under these capital leases were as follows (in thousands):


Fiscal year:
2019	$	883
2020		742
2021		656
2022		540
2023		529
Thereafter		1,868
Total minimum lease payments		5,218
Less amount representing interest		(749)
Capital lease obligations		4,469
Less current portion		(693)
Capital lease obligations, less current portion	$	3,776

The value of the equipment under capital leases as of December 31, 2018 was $6.1 million, with related accumulated amortization of $1.8 million.

The Company also leases certain fueling station equipment to a certain customer under a sales-type lease at an interest rate of 13.5%.

As of December 31, 2018, future receipts under this lease were as follows (in thousands):


Fiscal year:
2019	$	186
2020		186
2021		186
2022		186
2023		186
Thereafter		1,240
Capital lease receivables		2,170
Less amount representing interest		(1,080)
Capital lease receivables, less current portion	$	1,090

401(k) Plan	12 Months Ended
401(k) Plan	Dec. 31, 2019
Retirement Benefits [Abstract]
401(k) Plan	Note 18 —401(k) Plan The Company has established a savings plan (“Savings Plan”) which is qualified under Section 401(k) of the Internal Revenue Code. Eligible employees may elect to make contributions to the Savings Plan through salary deferrals of up to 90% of their base pay, subject to Internal Revenue Code limitations. The Company may also make discretionary contributions to the Savings Plans, subject to limitations. For each of the years ended December 31, 2017, 2018, and 2019 the Company contributed approximately $1.3 million of matching contributions to the Savings Plan.

Net Income (Loss) Per Share

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Net Income (Loss) Per Share

Note 19 – Net Income (Loss) Per Share

The following table sets forth the computations of basic and diluted earnings per share for the years ended December 31, 2017, 2018 and 2019 (in thousands, except share and per share amounts):


	2017		2018		2019
Net income (loss)	$	(79,237)	$	(3,790)	$	20,421

Weighted average common shares outstanding		150,430,239		180,655,435		204,573,287
Dilutive effect of potential common shares from restricted stock units and stock options		—		—		1,414,222
Weighted average common shares outstanding - diluted		150,430,239		180,655,435		205,987,509
Basic income (loss) per share	$	(0.53)	$	(0.02)	$	0.10
Diluted income (loss) per share	$	(0.53)	$	(0.02)	$	0.10

The following potentially dilutive securities have been excluded from the diluted net income (loss) per share calculations because their effect would have been antidilutive. Although these securities were antidilutive for these periods, they could be dilutive in future periods.


(in shares)	2017	2018	2019
Stock options	8,613,854	8,699,677	7,652,463
Convertibles notes	14,991,521	3,164,557	3,164,557
Restricted stock units	1,832,575	2,279,601	—

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transaction	Note 20 —Related Party Transactions During the year ended December 31, 2019, the Company sold RINs to a related party for proceeds of $1.7 million in the ordinary course of business. During the year ended December 31, 2019, the Company paid a related party $0.9 million for expenses incurred in the ordinary course of business and swap settlements on commodity swap contracts (Note 8 and Note 9). The amount due to the related party as of December 31, 2019 is immaterial.

Reportable Segments and Geographic Information

12 Months Ended

Dec. 31, 2019

Segment Reporting [Abstract]

Reportable Segments and Geographic Information

Note 21 —Reportable Segments and Geographic Information

Disclosures are required for certain information regarding operating segments, products and services, geographic areas of operation and major customers. Segment reporting is based upon the “management approach,” which assesses, how management organizes the Company’s operating segments for which separate financial information is (1) available and (2) evaluated regularly by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources and in assessing performance. The Company’s CODM is its Chief Executive Officer.

The Company operates in a single segment to sell natural gas. In making operating decisions, the CODM primarily considers consolidated financial information, accompanied by volumes delivered information. The assessment of operating results and the allocation of resources among the components of the business are made by the CODM and are based on gross margins and volumes delivered by market sector and volume type. Contracts are evaluated based on the economics of a mix of products and services for a customer.

The table below presents the Company’s revenue, operating income (loss) and long-lived assets by geographic area (in thousands). Several of the Company’s functions, including marketing, engineering, and finance are performed at the corporate level. As a result, significant interdependence and overlap exists among the Company’s geographic areas. Geographic revenue data reflect internal allocations and are therefore subject to certain assumptions and the Company’s methodology. Accordingly, revenue, operating income (loss), and long-lived assets shown for each geographic area may not be the amounts that would have been reported if the geographic areas were independent of one another. Revenue by geographic area is categorized based on where services are rendered and finished goods are sold. Operating income (loss) by geographic area is categorized based on the location of the entity selling the finished goods or providing the services. Long-lived assets by geographic are categorized based on the location of the assets.


	2017		2018		2019
Revenue:
United States	$	316,756	$	337,531	$	338,549
Canada		6,846		8,888		5,516
Other		17,997		—		—
Total revenue	$	341,599	$	346,419	$	344,065
Operating income (loss):
United States	$	(96,228)	$	3,548	$	10,805
Canada		(9,495)		347		(877)
Other		(28,724)		—		—
Total operating income (loss)	$	(134,447)	$	3,895	$	9,928
Long-lived assets:
United States	$	465,245	$	442,897	$	415,548
Canada		373		285		226
Other		—		—		—
Total long-lived assets	$	465,618	$	443,182	$	415,774

The Company’s goodwill and intangible assets as of December 31, 2017, 2018, and 2019 relate to its United States operations, and its subsidiaries, Clean Energy Cryogenics and NG Advantage (see Note 5).

Concentrations	12 Months Ended
Concentrations	Dec. 31, 2019
Risks and Uncertainties [Abstract]
Concentrations	Note 22 —Concentrations During the years ended December 31, 2017, 2018, and 2019, two, two, and three suppliers, respectively, each accounted for 10% or more of the Company’s natural gas expense related to CNG and LNG purchases. During the years ended December 31, 2017, 2018, and 2019, no single customer accounted for 10% or more of the Company’s total revenue.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Note 23 —Subsequent Events In February 2020, the Company converted the principal and accrued interest under the November 2019 Convertible Note into common units of NG Advantage resulting in an increase in the Company’s controlling interest in NG Advantage to 93.2%.

Schedule II: Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2019

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

Schedule II: Valuation and Qualifying Accounts

Schedule II - Valuation and Qualifying Accounts


	(In thousands)
	Allowances for		Allowance for
	Doubtful Trade		Doubtful Notes
	Receivables		Receivables
Balance as of December 31, 2016	$	1,063	$	1,230
Charges (benefit) to operations		395		3,344
Deductions		(182)		(30)
Balance as of December 31, 2017		1,276		4,544
Charges (benefit) to operations		1,169		—
Deductions		(526)		(381)
Balance as of December 31, 2018		1,919		4,163
Charges (benefit) to operations		908		931
Deductions		(415)		(1,763)
Balance as of December 31, 2019	$	2,412	$	3,331

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies

Basis of Presentation

Reclassifications

Use of Estimates

Inventory

Inventories consisted of the following as of December 31, 2018 and 2019 (in thousands):


	2018		2019
Raw materials and spare parts	$	34,890	$	29,874
Finished goods		85		—
Total inventory	$	34,975	$	29,874

Derivative Instruments and Hedging Activities

Property and Equipment

Long-Lived Assets

Finite-Lived Intangible Assets Amortization

The Company’s intangible assets as of December 31, 2018 and 2019 were as follows (in thousands):


	2018		2019
Customer relationships	$	5,376	$	5,376
Acquired contracts		4,384		4,384
Trademark and trade names		2,700		2,700
Non-compete agreements		860		860
Total intangible assets		13,320		13,320
Less accumulated amortization		(11,113)		(12,091)
Net intangible assets	$	2,207	$	1,229

Goodwill

During the years ended December 31, 2018 and 2019, the Company utilized the quantitative approach and concluded there were no indicators of impairment to goodwill.

The following table summarizes the activity related to the carrying amount of goodwill (in thousands):


Balance as of December 31, 2017	$	64,328
Balance as of December 31, 2018	$	64,328
Balance as of December 31, 2019	$	64,328

Revenue Recognition


	Balance as of		Adjustments		Balance as of
	December 31, 2017		due to ASC 606		January 1, 2018
Notes receivable and other long-term assets, net	$	21,397	$	(963)	$	20,434
Deferred revenue	$	3,432	$	330	$	3,762
Accumulated deficit	$	(683,570)	$	(1,293)	$	(684,863)

Volume-Related

Station Construction Sales

AFTC

Other

Alternative Fuels Tax Credit

LNG Transportation Costs

The Company records the costs incurred to transport LNG to its customers in “Product cost of sales” in the accompanying consolidated statements of operations.

Advertising Costs

Advertising costs are expensed as incurred. Advertising costs were $0.3 million, $0.9 million and $1.2 million for the years ended December 31, 2017, 2018, and 2019, respectively.

Stock-Based Compensation

Income Taxes

Net Income (Loss) Per Share

Foreign Currency Translation and Transactions

Comprehensive Loss

Comprehensive Income (Loss)

Concentration of Credit Risk

Recently Adopted Accounting Changes and Recently Issued Accounting Standards

Recently Adopted Accounting Changes

The effect of adopting ASC 842 was as follows (in thousands):


	Balance as of		Adjustments		Balance as of
	December 31, 2018		Due to ASC 842		January 1, 2019
Operating lease right-of-use assets	$	—	$	24,453	$	24,453
Operating lease obligations	$	—	$	25,943	$	25,943
Accrued liabilities	$	48,469	$	(496)	$	47,973
Other long-term liabilities	$	15,035	$	(994)	$	14,041

Recently Issued Accounting Standards

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Schedule of inventories

Inventories consisted of the following as of December 31, 2018 and 2019 (in thousands):


	2018		2019
Raw materials and spare parts	$	34,890	$	29,874
Finished goods		85		—
Total inventory	$	34,975	$	29,874

Schedule of finite-lived intangible assets

The Company’s intangible assets as of December 31, 2018 and 2019 were as follows (in thousands):


	2018		2019
Customer relationships	$	5,376	$	5,376
Acquired contracts		4,384		4,384
Trademark and trade names		2,700		2,700
Non-compete agreements		860		860
Total intangible assets		13,320		13,320
Less accumulated amortization		(11,113)		(12,091)
Net intangible assets	$	2,207	$	1,229

Schedule of goodwill

The following table summarizes the activity related to the carrying amount of goodwill (in thousands):


Balance as of December 31, 2017	$	64,328
Balance as of December 31, 2018	$	64,328
Balance as of December 31, 2019	$	64,328

ASC 606

Schedule of adoption adjustments


	Balance as of		Adjustments		Balance as of
	December 31, 2017		due to ASC 606		January 1, 2018
Notes receivable and other long-term assets, net	$	21,397	$	(963)	$	20,434
Deferred revenue	$	3,432	$	330	$	3,762
Accumulated deficit	$	(683,570)	$	(1,293)	$	(684,863)

ASC 842

Schedule of adoption adjustments

The effect of adopting ASC 842 was as follows (in thousands):


	Balance as of		Adjustments		Balance as of
	December 31, 2018		Due to ASC 842		January 1, 2019
Operating lease right-of-use assets	$	—	$	24,453	$	24,453
Operating lease obligations	$	—	$	25,943	$	25,943
Accrued liabilities	$	48,469	$	(496)	$	47,973
Other long-term liabilities	$	15,035	$	(994)	$	14,041

Revenue (Tables)

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

Schedule of disaggregation of revenue

The table below presents the Company’s revenue disaggregated by revenue source (in thousands):


	Years Ended December 31,
	2017		2018		2019
Volume-related (1)	$	264,880	$	286,684	$	273,535
Station construction sales		51,854		25,501		23,120
AFTC		—		26,729		47,123
Compressor sales (2)		23,527		—		—
Other		1,338		7,505		287
Total revenue	$	341,599	$	346,419	$	344,065

(2) The Company completed the CEC Combination (as defined in Note 4) during the year ended December 31, 2017 and no longer generates revenue from compressor sales.

Summary of contract balances

As of December 31, 2018 and 2019, the Company’s contract balances were as follows (in thousands):


	2018		2019
Accounts receivable, net	$	68,865	$	61,760

Contract assets - current	$	656	$	455
Contract assets - non-current		3,825		3,777
Contract assets - total	$	4,481	$	4,232

Contract liabilities - current	$	5,513	$	5,329
Contract liabilities - non-current		9,844		6,339
Contract liabilities - total	$	15,357	$	11,668

Asset Impairments, Other Charges, and Inventory Valuation Provision (Tables)

12 Months Ended

Dec. 31, 2019

Restructuring and Related Activities [Abstract]

Schedule of restructuring and impairment charges

The following table summarizes these charges (in thousands):


	Year Ended
	December 31, 2017
Workforce reduction and related charges	$	3,057
CEC asset impairments		32,274
Station closures and related charges		25,557
LCFS Credits charge		7,046
Total asset impairments and other charges		67,934
Inventory valuation provision		13,158
Total charges	$	81,092


			Cash Payments			Cash Payments				Cash Payments
			Made in the			Made in the				Made in the
			Year Ended	Balance as of		Year Ended		Balance as of		Year Ended		Balance as of
	Charges		December 31, 2017	December 31, 2017		December 31, 2018		December 31, 2018		December 31, 2019		December 31, 2019
Employee severance	$	2,757	(2,757)	$	—	$	—	$	—	$	—	$	—
Lease termination fees and AROs for station closures		4,083	(70)		4,013		(1,810)		2,203		(249)		1,954
	$	6,840	(2,827)	$	4,013	$	(1,810)	$	2,203	$	(249)	$	1,954

Investments in Other Entities and Noncontrolling Interest in a Subsidiary (Tables)

12 Months Ended

Dec. 31, 2019

Investments, All Other Investments [Abstract]

Summary of financial information

Summarized financial information for SAFE&CEC S.r.l. is as follows (in thousands):


	Year Ended December 31,
	2018		2019
Revenue	$	68,373	$	80,886
Gross profit	$	20,124	$	20,525
Operating income (loss)	$	(4,881)	$	1,207
Net income (loss)	$	(5,499)	$	93


	As of December 31,
	2018		2019
Current assets	$	42,568	$	56,765
Non-current assets		48,629		56,153
Total assets	$	91,197	$	112,918

Current liabilities	$	36,177	$	51,911
Non-current liabilities		6,955		11,952
Total liabilities	$	43,132	$	63,863

Cash, Cash Equivalents and Restricted Cash (Tables)

12 Months Ended

Dec. 31, 2019

Cash and Cash Equivalents [Abstract]

Schedule of cash and cash equivalents

Cash, cash equivalents and restricted cash as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Current assets:
Cash and cash equivalents	$	29,844	$	49,207
Restricted cash - standby letters of credit		30		15
Restricted cash - held in escrow		750		—
Total cash, cash equivalents and current portion of restricted cash	$	30,624	$	49,222

Long-term assets:
Restricted cash - standby letters of credit	$	4,000	$	4,000
Total long-term portion of restricted cash	$	4,000	$	4,000

Total cash, cash equivalents and restricted cash	$	34,624	$	53,222

Schedule of components of restricted cash

Cash, cash equivalents and restricted cash as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Current assets:
Cash and cash equivalents	$	29,844	$	49,207
Restricted cash - standby letters of credit		30		15
Restricted cash - held in escrow		750		—
Total cash, cash equivalents and current portion of restricted cash	$	30,624	$	49,222

Long-term assets:
Restricted cash - standby letters of credit	$	4,000	$	4,000
Total long-term portion of restricted cash	$	4,000	$	4,000

Total cash, cash equivalents and restricted cash	$	34,624	$	53,222

Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Summary of short-term investments

Short-term investments as of December 31, 2018 consisted of the following (in thousands):


			Gross
	Amortized		Unrealized		Estimated
	Cost		Losses		Fair Value
Municipal bonds and notes	$	9,210	$	(19)	$	9,191
Zero coupon bonds		29,823		(28)		29,795
Corporate bonds		26,175		(22)		26,153
Certificates of deposit		507		—		507
Total short-term investments	$	65,715	$	(69)	$	65,646

Short-term investments as of December 31, 2019 consisted of the following (in thousands):


			Gross
	Amortized		Unrealized		Estimated
	Cost		Losses		Fair Value
Municipal bonds and notes	$	2,986	$	—	$	2,986
Zero coupon bonds		33,919		—		33,919
Corporate bonds		19,509		(3)		19,506
Certificates of deposit		518		—		518
Total short-term investments	$	56,932	$	(3)	$	56,929

Derivative Instruments and Hedging Activities (Tables)

12 Months Ended

Dec. 31, 2019

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Summary of commodity derivative activity

Derivatives as of December 31, 2018 consisted of the following (in thousands):


	Gross Amounts		Gross Amounts		Net Amount
	Recognized		Offset		Presented
Assets:
Commodity swaps:
Current portion of derivative assets, related party	$	1,508	$	—	$	1,508
Long-term portion of derivative assets, related party		8,824		—		8,824
Total derivative assets	$	10,332	$	—	$	10,332

Derivatives and embedded derivatives as of as of December 31, 2019 consisted of the following (in thousands):


	Gross Amounts		Gross Amounts		Net Amount
	Recognized		Offset		Presented
Assets:
Commodity swaps:
Long-term portion of derivative assets, related party	$	3,270	$	—	$	3,270
Fueling agreements:
Prepaid expenses and other current assets		232		—		232
Notes receivable and other long-term assets, net		491		—		491
Total derivative assets	$	3,993	$	—	$	3,993
Liabilities:
Commodity swaps:
Current portion of derivative liabilities, related party	$	164	$	—	$	164
Fueling agreements:
Accrued liabilities		42		—		42
Other long-term liabilities		39		—		39
Total derivative liabilities	$	245	$	—	$	245

Schedule of weighted-average price of open commodity swap contract

The following table reflects the weighted-average price of open commodity swap contracts as of December 31, 2018 and 2019, by year with associated volumes:


	December 31, 2018			December 31, 2019
	Volumes	Weighted -Average Price per		Volumes	Weighted -average Price per
Year	(Diesel Gallons)	Diesel Gallon		(Diesel Gallons)	Diesel Gallon
2019	3,125,000	$	3.18	—	$	—
2020	5,000,000	$	3.18	4,986,000	$	2.37
2021	5,000,000	$	3.18	5,000,000	$	2.34
2022	5,000,000	$	3.18	5,000,000	$	2.34
2023	5,000,000	$	3.18	5,000,000	$	2.34
2024	1,875,000	$	3.18	1,870,000	$	1.76

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of inputs for fair value of outstanding commodity swap contracts

The Company estimated the fair value of its outstanding commodity swap contracts based on the following inputs as of December 31, 2018 and 2019:


	December 31, 2018			December 31, 2019
Significant Unobservable Inputs	Input Range	Weighted Average		Input Range	Weighted Average
ULSD Gulf Coast Forward Curve	$1.71 - $1.79	$	1.75	$1.76 - $1.88	$	1.81
Historical Differential to PADD 3 Diesel	$0.76 - $1.16	$	0.89	$0.79 - $1.16	$	0.91
Historical Differential to PADD 5 Diesel	$1.22 - $2.12	$	1.55	$1.32 - $2.30	$	1.78

The Company estimated the fair value of embedded derivatives in its fueling agreements under the Zero Now truck financing program based on the following inputs as of December 31, 2019:


	December 31, 2019
Significant Unobservable Inputs	Input Range	Weighted Average
ULSD Gulf Coast Forward Curve	$1.76 - $1.88	$	1.81
Historical Differential to PADD 5 Diesel	$1.32 - $2.30	$	1.78

Schedule of information by level for assets and liabilities that are measured at fair value on a recurring basis

The following tables provide information by level for assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2018 and 2019 (in thousands):


	December 31, 2018		Level 1		Level 2		Level 3
Assets:
Available-for-sale securities (1):
Municipal bonds and notes	$	9,191	$	—	$	9,191	$	—
Zero coupon bonds		29,795		—		29,795		—
Corporate bonds		26,153		—		26,153		—
Certificates of deposit (1)		507		—		507		—
Commodity swap contracts (2)		10,332		—		—		10,332
Embedded derivatives (3)		—		—		—		—
Liabilities:
Warrants (4)	$	1,079	$	—	$	—	$	1,079


	December 31, 2019		Level 1		Level 2		Level 3
Assets:
Available-for-sale securities (1):
Municipal bonds and notes	$	2,986	$	—	$	2,986	$	—
Zero coupon bonds		33,919		—		33,919		—
Corporate bonds		19,506		—		19,506		—
Certificates of deposit (1)		518		—		518		—
Commodity swap contracts (2)		3,270		—		—		3,270
Embedded derivatives (3)		723		—		—		723
Liabilities:
Commodity swap contracts (2)	$	164	$	—	$	—	$	164
Embedded derivatives (3)		81		—		—		81
Warrants (4)		40		—		—		40

(1)

Included in “Short-term investments” in the accompanying consolidated balance sheets. See Note 7 for more information.

(2)

(3)

Included in "Other long-term liabilities" as of December 31, 2018, and “Accrued liabilities” as of December 31, 2019 in the accompanying consolidated balance sheets.

Schedule of reconciliation of the beginning and ending balances of items measured at fair value on a recurring basis that used significant unobservable inputs (Level 3)


	Assets:		Assets:		Liabilities:		Liabilities:
	Commodity		Embedded		Commodity		Embedded		Liabilities:
	Swap Contracts		Derivatives		Swap Contracts		Derivatives		Warrants
Balance as of December 31, 2017	$	—	$	—	$	—	$	—	$	(536)
Total gain (loss)		10,332		—		—		—		(543)
Balance as of December 31, 2018	$	10,332	$	—	$	—	$	—	$	(1,079)

Balance as of December 31, 2018	$	10,332	$	—	$	—	$	—	$	(1,079)
Settlements, net		667		—		—		—		—
Total gain (loss)		(7,729)		723		(164)		(81)		1,039
Balance as of December 31, 2019	$	3,270	$	723	$	(164)	$	(81)	$	(40)

Change in unrealized gain (loss) for the year ended December 31, 2018 included in earnings	$	10,332	$	—	$	—	$	—	$	(543)
Change in unrealized gain (loss) for the year ended December 31, 2019 included in earnings	$	(7,062)	$	723	$	(164)	$	(81)	$	1,039

Other Receivables (Tables)

12 Months Ended

Dec. 31, 2019

Receivables [Abstract]

Schedule of other receivables

Other receivables as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Loans to customers to finance vehicle purchases	$	276	$	653
Accrued customer billings		6,261		6,124
Fuel tax credits		434		69,585
Other		8,573		8,536
Total other receivables	$	15,544	$	84,898

Land, Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Summary of land, property and equipment

Land, property and equipment, net as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Land	$	3,681	$	3,476
LNG liquefaction plants		94,633		94,633
Station equipment		319,119		324,431
Trailers		75,901		79,477
Other equipment		97,268		101,655
Construction in progress		73,485		75,232
		664,087		678,904
Less accumulated depreciation		(313,519)		(354,992)
Total land, property and equipment, net	$	350,568	$	323,912

Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2019

Payables and Accruals [Abstract]

Schedule of accrued liabilities

Accrued liabilities as of December 31, 2018 and 2019 consisted of the following (in thousands):


	2018		2019
Accrued alternative fuels incentives (1)	$	6,923	$	27,839
Accrued employee benefits		2,248		2,276
Accrued interest		78		220
Accrued gas and equipment purchases		12,833		11,383
Accrued property and other taxes		3,397		3,732
Accrued salaries and wages		8,609		9,105
Other (2)		14,381		13,142
Total accrued liabilities	$	48,469	$	67,697

(1)

Includes the amount of RINs, LCFS Credits and the amount of AFTC payable to third parties.

(2)

Debt (Tables)

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Schedule of long-term debt

Debt obligations as of December 31, 2018 and 2019 consisted of the following (in thousands):


	December 31, 2018
			Unamortized Debt		Balance, Net of
	Principal Balances		Financing Costs		Financing Costs
7.5% Notes	$	50,000	$	58	$	49,942
NG Advantage debt		28,904		155		28,749
Other debt		1,024		—		1,024
Total debt		79,928		213		79,715
Less amounts due within one year		(4,811)		(99)		(4,712)
Total long-term debt	$	75,117	$	114	$	75,003


	December 31, 2019
			Unamortized Debt		Balance, Net of
	Principal Balances		Financing Costs		Financing Costs
7.5% Notes	$	50,000	$	17	$	49,983
NG Advantage debt		33,898		192		33,706
SG Facility		4,400		—		4,400
Other debt		796		—		796
Total debt		89,094		209		88,885
Less amounts due within one year		(56,097)		(84)		(56,013)
Total long-term debt	$	32,997	$	125	$	32,872

Summary of aggregate maturities of long term debt and capital lease obligations

The following is a summary of the aggregate maturities of debt obligations for each of the yearly periods subsequent to December 31, 2019 (in thousands):


	2020		2021		2022		2023		2024		Thereafter		Total
7.5% Notes	$	50,000	$	—	$	—	$	—	$	—	$	—	$	50,000
NG Advantage debt		5,857		6,092		6,300		11,407		4,242		—		33,898
SG Facility		—		—		—		—		4,400		—		4,400
Other debt		240		248		215		93		—		—		796
Total	$	56,097	$	6,340	$	6,515	$	11,500	$	8,642	$	—	$	89,094

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2019

Stockholders' Equity Note [Abstract]

Summary of At-The-Market program activity

The following table summarizes the activity under the ATM Program for the periods presented:


	Year ended December 31,
(in 000s, except share amounts)	2017
Gross proceeds	$	10,767
Fees and issuance costs		311
Net proceeds	$	10,456
Shares issued		3,802,500

Summary of compensation expense and related income tax benefit related to the stock-based compensation expense recognized


	Year Ended December 31,
	2017		2018		2019
Stock-based compensation expense, net of $0 tax in 2017, 2018 and 2019 (1)	$	8,423	$	5,307	$	3,880

(1)

Summary of stock option activity

The following table summarizes the Company’s stock option activity for the year ended December 31, 2019:


				Weighted
				Average
		Weighted		Remaining	Aggregate
		Average		Contractual	Intrinsic
	Number of	Exercise		Term	Value
	Shares	Price		(in years)	(in thousands)
Options outstanding as of December 31, 2018	8,699,677	$	8.06
Granted	2,183,691		2.19
Exercised	(58,602)		1.79
Forfeited or expired	(1,703,101)		10.07
Options outstanding as of December 31, 2019	9,121,665	$	6.32	5.82	$	1,909
Options exercisable as of December 31, 2019	6,246,982	$	8.31	4.52	$	812
Options vested and expected to vest as of December 31, 2019	9,121,665	$	6.32	5.82	$	1,909

Schedule of assumptions used to estimate the fair value of each award using the Black-Scholes option pricing model

The fair value of each stock option granted was estimated as of the date of grant using the Black-Scholes option pricing model and using the following assumptions:


	Year Ended December 31,
	2017	2018	2019
Dividend yield	0.0%	0.0%	0.0%
Expected volatility	63.61%	70.2% to 74.6%	57.3% to 61.5%
Risk-free interest rate	2.05%	2.70% to 2.71%	2.11% to 2.53%
Expected life in years	6.0	6.0	6.0

Summary of the Company's RSU activity

The following table summarizes the Company’s Service-Based RSU activity for the year ended December 31, 2019:



		Weighted
		Average
	Number of	Fair Value at
	Shares	Grant Date
RSU outstanding as of December 31, 2018	2,279,601	$	1.88
Granted	—		—
Vested	(952,032)		2.13
Forfeited or expired	(95,764)		1.59
RSU outstanding and unvested as of December 31, 2019	1,231,805	$	1.71

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of components of income loss before income taxes

The components of income (loss) before income taxes for the years ended December 31, 2017, 2018, and 2019 are as follows (in thousands):


	2017		2018		2019
U.S.	$	(44,535)	$	(9,153)	$	14,981
Foreign		(38,770)		311		(864)
Total income (loss) before income taxes	$	(83,305)	$	(8,842)	$	14,117

Schedule of provision for income taxes

The provision for income taxes for the years ended December 31, 2017, 2018, and 2019 consists of the following (in thousands):


	2017		2018		2019
Current:
Federal	$	31	$	—	$	—
State		231		341		116
Foreign		224		—		4
Total current		486		341		120
Deferred:
Federal		(978)		—		293
State		(184)		—		445
Foreign		(1,238)		—		—
Total deferred		(2,400)		—		738
Total expense (benefit)	$	(1,914)	$	341	$	858

Schedule of reconciliation of federal income tax rate to the actual effective tax rate

Income tax expense (benefit) for the years ended December 31, 2017, 2018, and 2019 differs from the “expected” amount computed using the federal income tax rate of 35% as of December 31, 2017 and 21% as of December 31, 2018 and 2019 as a result of the following (in thousands):


	2017		2018		2019
Computed expected tax (benefit)	$	(29,157)	$	(1,857)	$	2,964
Nondeductible expenses		13,420		5,674		3,087
Tax rate differential on foreign earnings		11,860		(56)		245
Joint ventures		—		947		(369)
Noncontrolling interest		—		1,133		4,114
Impact of federal income tax rate change		59,729		—		—
Tax credits		(27)		(6,603)		(10,314)
Other		2,376		985		665
Change in valuation allowance		(60,115)		118		466
Total tax expense (benefit)	$	(1,914)	$	341	$	858

Schedule of tax effect of temporary differences that give rise to deferred tax assets and liabilities

The tax effect of temporary differences that give rise to deferred tax assets and liabilities as of December 31, 2018 and 2019 are as follows (in thousands):


	2018		2019
Deferred tax assets:
Accrued expenses	$	5,254	$	4,899
Alternative minimum tax and general business credits		6,801		6,651
Stock option expense		11,210		9,254
Other		1,998		1,456
Loss carryforwards		106,957		107,722
Total deferred tax assets		132,220		129,982
Less valuation allowance		(120,801)		(122,147)
Net deferred tax assets		11,419		7,835
Deferred tax liabilities:
Commodity swap contracts		(2,751)		(998)
Depreciation and amortization		(2,672)		(911)
Goodwill		(1,650)		(1,910)
Investments in joint ventures and partnerships		(4,346)		(4,754)
Total deferred tax liabilities		(11,419)		(8,573)
Net deferred tax liabilities	$	—	$	(738)

Schedule of reconciliation of the total amounts of unrecognized tax benefits

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits for the years ended December 31, 2017, 2018, and 2019 (in thousands):


Unrecognized tax benefit—December 31, 2017	$	34,065
Gross increases—tax positions in current year		2,178
Unrecognized tax benefit—December 31, 2018		36,243
Gross increases—tax positions in current year		5,232
Unrecognized tax benefit—December 31, 2019	$	41,475

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases

Schedule of finance and operating lease asset and liability balances

As of December 31, 2019, the Company’s finance and operating lease asset and liability balances were as follows (in thousands):


	2019
Finance leases:
Land, property and equipment, gross	$	5,177
Accumulated depreciation		(2,134)
Land, property and equipment, net	$	3,043

Current portion of finance lease obligations	$	615
Long-term portion of finance lease obligations		2,715
Total finance lease liabilities	$	3,330

Operating leases:
Operating lease right-of-use assets (1)	$	28,627

Current portion of operating lease obligations	$	3,359
Long-term portion of operating lease obligations		26,206
Total operating lease liabilities	$	29,565

The Company’s operating lease ROU assets are comprised of the following (in thousands):


	December 31, 2019
	Assets		Liabilities
Real estate for fueling stations	$	17,978	$	17,978
LNG plant, office spaces and warehouses		10,624		11,562
Office equipment		25		25
Total operating lease right-of-use assets	$	28,627	$	29,565

Schedule of components of lease expense for finance and operating lease liabilities and supplemental information

The components of lease expense for finance and operating leases consisted of the following (in thousands):


	Year Ended
	December 31, 2019
Finance leases:
Depreciation on assets under finance leases	$	498
Interest on lease liabilities		189
Total finance leases expense	$	687

Operating leases:
Lease expense	$	6,630
Lease expense on short-term leases		1,950
Variable lease expense		2,755
Sublease income		(206)
Total operating leases expense	$	11,129

Supplemental information on finance and operating leases is as follows (dollars in thousands):


	Year Ended
	December 31, 2019
Operating cash outflows from finance leases	$	189
Operating cash outflows from operating leases	$	5,350
Financing cash outflows from finance leases	$	1,667

Assets obtained in exchange for new finance lease liabilities (1)	$	519
ROU assets obtained in exchange for operating lease liabilities (1)	$	31,861


		December 31, 2019
Weighted-average remaining lease term - finance leases		4.49 years
Weighted-average remaining lease term - operating leases		11.10 years

Weighted-average discount rate - finance leases		5.09%
Weighted-average discount rate - operating leases		8.29%

Schedule of maturities of operating lease liabilities

The following schedule represents the Company’s maturities of finance and operating lease liabilities as of December 31, 2019 (in thousands):


	Finance Leases		Operating Leases
Fiscal year:
2020	$	767	$	5,484
2021		679		4,658
2022		560		3,736
2023		462		3,712
2024		1,026		3,704
Thereafter		314		25,208
Total minimum lease payments		3,808		46,502
Less amount representing interest		(478)		(16,937)
Present value of lease liabilities	$	3,330	$	29,565

Schedule of maturities of finance lease liabilities


	Finance Leases		Operating Leases
Fiscal year:
2020	$	767	$	5,484
2021		679		4,658
2022		560		3,736
2023		462		3,712
2024		1,026		3,704
Thereafter		314		25,208
Total minimum lease payments		3,808		46,502
Less amount representing interest		(478)		(16,937)
Present value of lease liabilities	$	3,330	$	29,565

Schedule of maturities of lease receivables

The following schedule represents the Company’s maturities of lease receivables as of December 31, 2019 (in thousands):


Fiscal year:
2020	$	186
2021		186
2022		186
2023		186
2024		186
Thereafter		1,054
Total minimum lease payments		1,984
Less amount representing interest		(935)
Present value of lease receivables	$	1,049

Schedule of future minimum lease obligations for all noncancelable operating leases

The following schedule represents the Company’s future minimum lease obligations under all noncancelable operating leases as of December 31, 2018 (in thousands):


Fiscal year:
2019	$	6,340
2020		4,332
2021		3,311
2022		2,409
2023		2,300
Thereafter		13,214
Total future minimum lease payments	$	31,906

Schedule of future payments under the capital leases

As of December 31, 2018, future payments under these capital leases were as follows (in thousands):


Fiscal year:
2019	$	883
2020		742
2021		656
2022		540
2023		529
Thereafter		1,868
Total minimum lease payments		5,218
Less amount representing interest		(749)
Capital lease obligations		4,469
Less current portion		(693)
Capital lease obligations, less current portion	$	3,776

Schedule of future receipts under the leases

As of December 31, 2018, future receipts under this lease were as follows (in thousands):


Fiscal year:
2019	$	186
2020		186
2021		186
2022		186
2023		186
Thereafter		1,240
Capital lease receivables		2,170
Less amount representing interest		(1,080)
Capital lease receivables, less current portion	$	1,090

Net Income (Loss) Per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of information required to compute basic and diluted net loss per share

The following table sets forth the computations of basic and diluted earnings per share for the years ended December 31, 2017, 2018 and 2019 (in thousands, except share and per share amounts):


	2017		2018		2019
Net income (loss)	$	(79,237)	$	(3,790)	$	20,421

Weighted average common shares outstanding		150,430,239		180,655,435		204,573,287
Dilutive effect of potential common shares from restricted stock units and stock options		—		—		1,414,222
Weighted average common shares outstanding - diluted		150,430,239		180,655,435		205,987,509
Basic income (loss) per share	$	(0.53)	$	(0.02)	$	0.10
Diluted income (loss) per share	$	(0.53)	$	(0.02)	$	0.10

Schedule of potentially dilutive securities that have been excluded from the diluted net loss per share calculations because their effect would have been antidilutive


(in shares)	2017	2018	2019
Stock options	8,613,854	8,699,677	7,652,463
Convertibles notes	14,991,521	3,164,557	3,164,557
Restricted stock units	1,832,575	2,279,601	—

Reportable Segments and Geographic Information (Tables)

12 Months Ended

Dec. 31, 2019

Segment Reporting [Abstract]

Schedule of revenue, operating income (loss), and long-lived assets shown for each geographic area


	2017		2018		2019
Revenue:
United States	$	316,756	$	337,531	$	338,549
Canada		6,846		8,888		5,516
Other		17,997		—		—
Total revenue	$	341,599	$	346,419	$	344,065
Operating income (loss):
United States	$	(96,228)	$	3,548	$	10,805
Canada		(9,495)		347		(877)
Other		(28,724)		—		—
Total operating income (loss)	$	(134,447)	$	3,895	$	9,928
Long-lived assets:
United States	$	465,245	$	442,897	$	415,548
Canada		373		285		226
Other		—		—		—
Total long-lived assets	$	465,618	$	443,182	$	415,774

Summary of Significant Accounting Policies - Reclassifications (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2018
Summary of Significant Accounting Policies
Current portion of finance lease obligations	$ 615		$ 693
Long-term portion of finance lease obligations	2,715		$ 3,776
Deferred income taxes	$ 738	$ (2,400)

Summary of Significant Accounting Policies - Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventories
Raw materials and spare parts	$ 29,874	$ 34,890
Finished goods		85
Total inventory	$ 29,874	$ 34,975

Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Proceeds from grants	$ 1.6	$ 0.7	$ 4.4
LNG liquefaction plants \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
LNG liquefaction plants \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	20 years
Station equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Other equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Other equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	7 years

Summary of Significant Accounting Policies - Long-Lived Assets (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and intangible assets
Long-lived intangible impairment		$ 0	$ 0	$ 32,300,000
Total intangible assets		13,320,000	13,320,000
Less accumulated amortization		(12,091,000)	(11,113,000)
Net intangible assets		1,229,000	2,207,000
Amortization expense		1,000,000	1,400,000	$ 5,100,000
Estimated amortization expense
2020		800,000
2021		500,000
Customer relationships
Goodwill and intangible assets
Total intangible assets		$ 5,376,000	5,376,000
Customer relationships \| Minimum
Goodwill and intangible assets
Estimated useful lives		1 year
Customer relationships \| Maximum
Goodwill and intangible assets
Estimated useful lives		8 years
Acquired contracts
Goodwill and intangible assets
Total intangible assets		$ 4,384,000	4,384,000
Acquired contracts \| Minimum
Goodwill and intangible assets
Estimated useful lives		1 year
Acquired contracts \| Maximum
Goodwill and intangible assets
Estimated useful lives		10 years
Trademark and trade names
Goodwill and intangible assets
Total intangible assets		$ 2,700,000	2,700,000
Trademark and trade names \| Minimum
Goodwill and intangible assets
Estimated useful lives		2 years
Trademark and trade names \| Maximum
Goodwill and intangible assets
Estimated useful lives		10 years
Non-compete agreements
Goodwill and intangible assets
Estimated useful lives		3 years
Total intangible assets		$ 860,000	$ 860,000
Facility Closing
Goodwill and intangible assets
Long-lived intangible impairment	$ 20,400,000
CEC
Goodwill and intangible assets
Long-lived intangible impairment	$ 32,300,000

Summary of Significant Accounting Policies - Goodwill (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($) item	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Summary of Significant Accounting Policies
Number of reporting units \| item	1
Goodwill \| $	$ 64,328	$ 64,328	$ 64,328

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 02, 2018	Jan. 01, 2018
Notes receivable and other long-term assets, net	$ 31,622	$ 17,470	$ 21,397	$ 20,434
Deferred Revenue	7,338	7,361	3,432	3,762
Retained Earnings (Accumulated Deficit)	(668,232)	(688,653)	(683,570)	$ (684,863)
Difference between Revenue Guidance in Effect before and after Topic 606
Notes receivable and other long-term assets, net					$ (963)
Deferred Revenue					330
Retained Earnings (Accumulated Deficit)					$ (1,293)
Commodity Swap And Customer Contract [Member]
Total gain (loss)	$ (6,600)	$ 10,300	$ 0

Summary of Significant Accounting Policies - Alternative Fuels Tax Credit (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / gal	Dec. 31, 2018 USD ($) $ / gal	Dec. 31, 2017 USD ($) $ / gal
Summary of Significant Accounting Policies
Federal fuel tax credit - CNG (in dollars per gasoline gallon equivalent) \| $ / gal	0.50	0.50	0.50
Federal fuel tax credit - LNG (in dollars per liquid gallon) \| $ / gal	0.50	0.50	0.50
VETC credits recognized as revenue \| $	$ 47.1	$ 25.2	$ 0.0
VETC credits recognized as revenue from prior years \| $		$ 1.5

Summary of Significant Accounting Policies - Advertising Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Advertising expense	$ 1.2	$ 0.9	$ 0.3

Summary of Significant Accounting Policies - Stock-Based Compensation (Details) $ in Millions	Jan. 01, 2017 USD ($)
Accounting Standards Update 2016-09 \| Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption	$ 0.2

Summary of Significant Accounting Policies - Income Taxes (Details) $ in Millions	Jan. 01, 2017 USD ($)
Accumulated Deficit \| Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption	$ 0.3

Summary of Significant Accounting Policies - Foreign Currency Translation and Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Foreign exchange transactions gains (losses) included in other income (expense)	$ 0.0	$ 0.0	$ (0.2)

Summary of Significant Accounting Policies - Recently Adopted Accounting Changes and Recently Issued Accounting Standards (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 02, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 28,627	$ 24,453
Operating lease obligations	29,565	25,943
Accrued liabilities	67,697	47,973		$ 48,469
Other long-term liabilities	$ 9,701	$ 14,041		$ 15,035
ASC 842 \| Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets			$ 24,453
Operating lease obligations			25,943
Accrued liabilities			(496)
Other long-term liabilities			$ (994)

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contracts with Customers
Revenue	$ 344,065	$ 346,419	$ 341,599
Receivables, net	61,760	68,865
Contract Assets - Current	455	656
Contract Assets - Noncurrent	3,777	3,825
Contract Assets - Total	4,232	4,481
Contract Liabilities - Current	5,329	5,513
Contract Liabilities - Noncurrent	6,339	9,844
Contract Liabilities - Total	11,668	15,357
Commodity Swap And Customer Contract [Member]
Revenue from Contracts with Customers
Total gain (loss)	(6,600)	10,300	0
Volume -Related
Revenue from Contracts with Customers
Revenue	273,535	286,684	264,880
Contract Liabilities - Current	3,500	3,500
Volume -Related \| Commodity Swap And Customer Contract [Member]
Revenue from Contracts with Customers
Total gain (loss)	(6,600)	10,300
Station construction sales
Revenue from Contracts with Customers
Revenue	23,120	25,501	51,854
Contract Liabilities - Current	1,800	2,000
AFTC
Revenue from Contracts with Customers
Revenue	47,123	26,729
Compressor sales
Revenue from Contracts with Customers
Revenue			23,527
Other
Revenue from Contracts with Customers
Revenue	$ 287	$ 7,505	$ 1,338

Revenue - Remaining Performance Obligations (Details) $ in Millions	Dec. 31, 2019 USD ($)
Remaining Performance Obligations
Revenue, remaining performance obligation, amount	$ 15.8
Minimum \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Remaining Performance Obligations
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months
Maximum \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Remaining Performance Obligations
Revenue, remaining performance obligation, expected timing of satisfaction, period	24 months

Revenue - Contract Costs and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contracts with Customers
Capitalized contract cost, gross	$ 10,200	$ 9,100
Capitalized contract cost, accumulated depreciation	6,300	4,900
Capitalized contract cost, amortization	2,200	2,000
Contract Liabilities - Current	5,329	5,513
Contract with customer, liability, revenue recognized	5,900
Station construction sales
Revenue from Contracts with Customers
Contract Liabilities - Current	1,800	2,000
Volume -Related
Revenue from Contracts with Customers
Contract Liabilities - Current	$ 3,500	$ 3,500

Asset Impairments, Other Charges, and Inventory Valuation Provision - Summary of Charges (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Workforce reduction and related charges		$ 3,057
CEC asset impairments		32,274
Station closures and related charges		25,557
LCFS Credits charge	$ 7,000	7,046
Total asset impairments and other charges		67,934
Inventory valuation provision		13,158
Total charges		$ 81,092

Asset Impairments, Other Charges, and Inventory Valuation Provision (Details)	3 Months Ended		12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) item	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Cash Charges
Restructuring charges					$ 6,840,000
Long-lived intangible impairment			$ 0	$ 0	32,300,000
Impaired long-lived assets	$ 465,618,000		$ 415,774,000	$ 443,182,000	465,618,000
Asset impairments and other charges					67,934,000
Inventory valuation provision					13,158,000
LCFS Credits charge	7,000,000				7,046,000
Discontinued Operations, Held-for-sale or Disposed of by Sale \| Station Closures
Cash Charges
Inventory held-for-sale	$ 27,200,000				27,200,000
Inventory valuation provision					7,800,000
Employee Severance
Cash Charges
Restructuring charges					2,757,000
Stock-based compensation expense					300,000
Facility Closing
Cash Charges
Long-lived intangible impairment		$ 20,400,000
Other restructuring charges		$ 5,200,000
Facility Closing \| Natural Gas Fueling Stations
Cash Charges
Number of natural gas fueling stations, intended closures \| item		42
Facility Closing \| Natural Gas Fueling Stations \| Fair Value, Measurements, Nonrecurring \| Level 3
Cash Charges
Impaired long-lived assets		$ 23,300,000
Impaired long-lived assets, fair value		2,900,000
Asset impairments and other charges		$ 20,400,000
Strategic shift in operations
Cash Charges
Inventory valuation provision					$ 5,400,000

Asset Impairments, Other Charges, and Inventory Valuation Provision - Cash Charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Charges
Charges			$ 6,840
Restructuring Reserve [Roll Forward]
Balance as of Beginning of the period	$ 2,203	$ 4,013
Cash Payments Made	(249)	(1,810)	(2,827)
Balance as of End of period	1,954	2,203	4,013
Employee Severance
Cash Charges
Charges			2,757
Restructuring Reserve [Roll Forward]
Cash Payments Made			(2,757)
Lease termination fees and AROs for station closures
Cash Charges
Charges			4,083
Restructuring Reserve [Roll Forward]
Balance as of Beginning of the period	2,203	4,013
Cash Payments Made	(249)	(1,810)	(70)
Balance as of End of period	$ 1,954	$ 2,203	$ 4,013

Divestitures - BP Transaction (Details) $ in Thousands					1 Months Ended		9 Months Ended	12 Months Ended			21 Months Ended
Divestitures - BP Transaction (Details) $ in Thousands	Mar. 01, 2019 USD ($)	Jun. 22, 2017 USD ($)	Mar. 31, 2017 USD ($)	Feb. 27, 2017 USD ($) facility	Dec. 31, 2019 USD ($)	Feb. 28, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)
Acquisitions and Divestitures
Asset purchase agreement, gain from sale of certain assets of subsidiary								$ 7,455	$ 4,782	$ 70,658
Goodwill					$ 64,328		$ 64,328	64,328	64,328	64,328	$ 64,328
BP Products North America, Inc.
Acquisitions and Divestitures
Production facilities to be developed \| facility				2
Asset purchase agreement, amount			$ 155,500
Extinguishment of debt, amount			8,800
Asset purchase agreement, cash paid	$ 5,400		30,000			$ 900	1,000
Asset purchase agreement, accrued amount					900			900
Asset purchase agreement, debt instrument, face amount			123,500
Asset purchase agreement, post-closing adjustments, payment		$ 2,000
Asset purchase agreement, gain from sale of certain assets of subsidiary					8,400					70,700	$ 800
Goodwill							26,600			26,600
Asset purchase agreement, contingent consideration (up to)				$ 25,000				7,500	$ 4,800	$ 800
Asset purchase agreement, contingent consideration, term				5 years
Asset purchase agreement, payment of transaction costs			$ 3,700		$ 2,800	$ 100	$ 9,200	$ 600
Asset purchase agreement, shares issued (in shares) \| shares						15,877	770,269
Asset purchase agreement, shares issued, value						$ 0	$ 2,000
Proceeds from sale of other assets							$ 142,200
Maximum \| BP Products North America, Inc.
Acquisitions and Divestitures
Asset purchase agreement, contingent consideration, term					5 years
Minimum \| BP Products North America, Inc.
Acquisitions and Divestitures
Asset purchase agreement, contingent consideration, term					4 years

Divestitures - SAFE&CEC S.r.l. (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 29, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 02, 2019
Acquisitions and Divestitures
Gain from sale of certain assets of subsidiary		$ 7,455	$ 4,782	$ 70,658
Working capital adjustments, funding for certain post-closing commitments, and transaction fees		13,142	14,381
Loss before income taxes		(14,117)	8,842	83,305
Accrued liabilities		67,697	48,469		$ 47,973
Income (loss) from equity method investments		(119)	(2,723)	(131)
CEC
Acquisitions and Divestitures
Loss before income taxes				45,100
SAFE&CEC S.r.l.
Acquisitions and Divestitures
Ownership interest (as a percent)	49.00%
Gain from sale of certain assets of subsidiary				$ 6,500
Working capital adjustments, funding for certain post-closing commitments, and transaction fees		1,000	3,300
Goodwill reduced during the year	$ 3,600
Accrued liabilities		1,200
Income (loss) from equity method investments		0	(2,900)
Investment balance		$ 23,700	$ 23,400
SAFE&CEC S.r.l. \| Landi Renzo S.p.A.
Acquisitions and Divestitures
Ownership interest (as a percent)	51.00%

Investments in Other Entities and Noncontrolling Interest in a Subsidiary - SAFE&CEC S.r.l. (Details) - SAFE&CEC S.r.l. - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 29, 2017
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)			49.00%
Equity Method Investment, Summarized Financial Information [Abstract]
Revenue	$ 80,886	$ 68,373
Gross profit	20,525	20,124
Operating income (loss)	1,207	(4,881)
Net income (loss)	93	(5,499)
Current assets	56,765	42,568
Non-current assets	56,153	48,629
Total assets	112,918	91,197
Current liabilities	51,911	36,177
Non-current liabilities	11,952	6,955
Total liabilities	$ 63,863	$ 43,132

Investments in Other Entities and Noncontrolling Interest in a Subsidiary - MCEP (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 16, 2014
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	$ (119)	$ (2,723)	$ (131)
Mansfield Clean Energy Partners LL
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)				50.00%
Income (loss) from equity method investments	(100)	200	$ (100)
Investment balance	$ 1,600	$ 1,700

- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References + Details

Investments in Other Entities and Noncontrolling Interest in a Subsidiary - NG Advantage (Details) - USD ($) $ in Thousands								1 Months Ended					4 Months Ended	5 Months Ended	12 Months Ended
	Nov. 27, 2019	Jun. 28, 2019	Jun. 11, 2019	Apr. 15, 2019	Feb. 15, 2019	Oct. 01, 2018	Feb. 28, 2018	Dec. 31, 2019	Feb. 28, 2019	Jan. 31, 2019	Dec. 31, 2018	Nov. 30, 2018	Feb. 28, 2019	Nov. 26, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 11, 2019	May 17, 2019	Jul. 14, 2017	Oct. 14, 2014
Business Acquisition [Line Items]
Payments to acquire additional interest in subsidiaries																	$ 1,928
Outstanding balance								$ 88,885			$ 79,715				$ 88,885	$ 79,715
Income (loss) attributable to noncontrolling interest															$ (7,162)	$ (5,393)	(2,154)
NG Advantage
Business Acquisition [Line Items]
Purchase of interest by parent, shares purchased (in shares)						1,000,001
Payments to acquire additional interest in subsidiaries						$ 5,000
Ownership interest before transaction (as a percent)						53.50%	53.30%									63.00%
Ownership interest after transaction (as a percent)						61.70%	53.50%								64.60%
Income (loss) attributable to noncontrolling interest															$ (7,200)	$ (5,400)	$ (2,200)
Noncontrolling interest								9,600			$ 17,000				9,600	$ 17,000
NG Advantage \| 2019 Note
Business Acquisition [Line Items]
Debt Instrument, Face Amount					$ 5,000
Proceeds from issuance of debt				$ 2,500	$ 2,500
NG Advantage \| 2019 Bridge Loan
Business Acquisition [Line Items]
Debt Instrument, Face Amount																			$ 500
Proceeds from issuance of debt			$ 100
NG Advantage \| June 2019 Convertible Note
Business Acquisition [Line Items]
Debt Instrument, Face Amount		$ 15,200
Proceeds from issuance of debt		$ 3,500												$ 7,400
Number of common units to be called by warrants (in shares)		86,879
NG Advantage \| November 2019 Convertible Note
Business Acquisition [Line Items]
Debt Instrument, Face Amount	$ 26,700
Proceeds from Convertible Debt	$ 3,400							6,600
Number of common units to be called by warrants (in shares)	2,000,000
Interest rate (as a percent)																		12.00%
Outstanding balance								$ 26,700							$ 26,700
NG Advantage \| Payment Obligations
Business Acquisition [Line Items]
Aggregate payment obligation guaranty							$ 30,000
Purchase of interest by parent, shares purchased (in shares)							19,660		100,000	100,000	100,000	100,000	400,000
NG Advantage
Business Acquisition [Line Items]
Ownership interest (as a percent)																				53.30%	53.30%
Aggregate value of stock																				$ 7,500

Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash
Cash and cash equivalents	$ 49,207	$ 29,844
Total cash, cash equivalents and current portion of restricted cash	49,222	30,624
Long-term portion of restricted cash	4,000	4,000
Total cash, cash equivalents and restricted cash	53,222	34,624	$ 37,208	$ 43,115
Amount in excess of FDIC and CDIC limits	47,900	28,500
Held in Escrow [Member]
Restricted Cash
Restricted cash		750
Standby letters of credit
Restricted Cash
Restricted cash	15	30
Long-term portion of restricted cash	$ 4,000	$ 4,000

Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 56,932	$ 65,715
Gross Unrealized Losses	(3)	(69)
Estimated Fair Value	56,929	65,646
Municipal bonds and notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,986	9,210
Gross Unrealized Losses		(19)
Estimated Fair Value	2,986	9,191
Zero coupon bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	33,919	29,823
Gross Unrealized Losses		(28)
Estimated Fair Value	33,919	29,795
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	19,509	26,175
Gross Unrealized Losses	(3)	(22)
Estimated Fair Value	19,506	26,153
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	518	507
Estimated Fair Value	$ 518	$ 507

Derivative Instruments and Hedging Activities (Details) - Not Designated as Hedging Instrument - Commodity swap contracts	1 Months Ended	12 Months Ended
	Oct. 31, 2018 contract gal	Dec. 31, 2019 $ / gal gal	Dec. 31, 2018 $ / gal gal
Derivative [Line Items]
Derivative asset, number of instruments held \| contract	2
Volumes (Diesel Gallons) \| gal	5,000,000	21,900,000	25,000,000
Weighted -average price per diesel gallon (in usd per gallon) \| $ / gal		2.30	3.18

Derivative Instruments and Hedging Activities - Summary of Commodity Derivative Activity (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivative Assets
Gross Amounts Recognized	$ 3,993	$ 10,332
Net Amount Presented	3,993	10,332
Derivative Liability
Gross Amounts Recognized	245
Net Amount Presented	245
Current portion of derivative assets, related party \| Commodity swap contracts
Derivative Assets
Gross Amounts Recognized		1,508
Net Amount Presented		1,508
Long-term portion of derivative assets, related party \| Commodity swap contracts
Derivative Assets
Gross Amounts Recognized	3,270	8,824
Net Amount Presented	3,270	$ 8,824
Current portion of derivative liabilities, related party \| Commodity swap contracts
Derivative Liability
Gross Amounts Recognized	164
Net Amount Presented	164
Prepaid expenses and other current assets \| Fueling agreements
Derivative Assets
Gross Amounts Recognized	232
Net Amount Presented	232
Notes receivable and other long-term assets, net \| Fueling agreements
Derivative Assets
Gross Amounts Recognized	491
Net Amount Presented	491
Accrued liabilities \| Fueling agreements
Derivative Liability
Gross Amounts Recognized	42
Net Amount Presented	42
Other long-term liabilities \| Fueling agreements
Derivative Liability
Gross Amounts Recognized	39
Net Amount Presented	$ 39

Derivative Instruments and Hedging Activities - Schedule of Weighted-Average Price of Open Commodity Wwap Contracts (Details) - Not Designated as Hedging Instrument	12 Months Ended
	Dec. 31, 2019 $ / gal gal	Dec. 31, 2018 $ / gal gal
Commodity Swap 2019
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal		3,125,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal		3.18
Commodity Swap 2020
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	4,986,000	5,000,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	2.37	3.18
Commodity Swap 2021
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	5,000,000	5,000,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	2.34	3.18
Commodity Swap 2022
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	5,000,000	5,000,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	2.34	3.18
Commodity Swap 2023
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	5,000,000	5,000,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	2.34	3.18
Commodity Swap 2024
Derivative [Line Items]
Volumes (Diesel Gallons) \| gal	1,870,000	1,875,000
Weighted -Average Price per Diesel Gallon (in usd per gallon) \| $ / gal	1.76	3.18

Fair Value Measurements - Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Available-for-sale securities	$ 56,929	$ 65,646
Short-term investments	56,929	65,646
Municipal bonds and notes
Assets:
Available-for-sale securities	2,986	9,191
Zero coupon bonds
Assets:
Available-for-sale securities	33,919	29,795
Corporate bonds
Assets:
Available-for-sale securities	19,506	26,153
Certificates of deposit
Assets:
Available-for-sale securities	518	507
Fair value measured on recurring basis \| Municipal bonds and notes
Assets:
Available-for-sale securities	2,986	9,191
Fair value measured on recurring basis \| Zero coupon bonds
Assets:
Available-for-sale securities	33,919	29,795
Fair value measured on recurring basis \| Corporate bonds
Assets:
Available-for-sale securities	19,506	26,153
Fair value measured on recurring basis \| Certificates of deposit
Assets:
Short-term investments	518	507
Fair value measured on recurring basis \| Commodity swap contracts
Assets:
Derivative assets	3,270	10,332
Liabilities:
Derivative liabilities	164
Fair value measured on recurring basis \| Embedded derivatives
Assets:
Derivative assets	723
Liabilities:
Derivative liabilities	81
Fair value measured on recurring basis \| Warrants
Liabilities:
Derivative liabilities	40	1,079
Fair value measured on recurring basis \| Level 2 \| Municipal bonds and notes
Assets:
Available-for-sale securities	2,986	9,191
Fair value measured on recurring basis \| Level 2 \| Zero coupon bonds
Assets:
Available-for-sale securities	33,919	29,795
Fair value measured on recurring basis \| Level 2 \| Corporate bonds
Assets:
Available-for-sale securities	19,506	26,153
Fair value measured on recurring basis \| Level 2 \| Certificates of deposit
Assets:
Short-term investments	518	507
Fair value measured on recurring basis \| Level 3 \| Commodity swap contracts
Assets:
Derivative assets	3,270	10,332
Liabilities:
Derivative liabilities	164
Fair value measured on recurring basis \| Level 3 \| Embedded derivatives
Assets:
Derivative assets	723
Liabilities:
Derivative liabilities	81
Fair value measured on recurring basis \| Level 3 \| Warrants
Liabilities:
Derivative liabilities	$ 40	$ 1,079

Fair Value Measurements - Fair Value Recognition - Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Commodity swap contracts
Reconciliation of the beginning and ending balances of assets measured at fair value using significant unobservable inputs (Level 3)
Beginning balance	$ 10,332
Settlements, net	667
Total gain (loss)	7,729	$ (10,332)
Ending balance	3,270	10,332
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(7,062)	$ 10,332
Embedded derivatives
Reconciliation of the beginning and ending balances of assets measured at fair value using significant unobservable inputs (Level 3)
Total gain (loss)	723
Ending balance	723
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 723

Fair Value Measurements - Fair Value Recognition - Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Commodity swap contracts
Reconciliation of the beginning and ending balances of liabilities measured at fair value using significant unobservable inputs (Level 3)
Total gain (loss)	$ (164)
Ending Balance	(164)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(164)
Embedded derivatives
Reconciliation of the beginning and ending balances of liabilities measured at fair value using significant unobservable inputs (Level 3)
Total gain (loss)	(81)
Ending Balance	(81)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(81)
Warrants
Reconciliation of the beginning and ending balances of liabilities measured at fair value using significant unobservable inputs (Level 3)
Beginning Balance	(1,079)	$ 536
Total gain (loss)	1,039	(543)
Ending Balance	(40)	(1,079)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 1,039	$ (543)

Other Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Receivables
Other receivables	$ 84,898	$ 15,544
Loans to customers to finance vehicle purchases
Other Receivables
Other receivables	653	276
Accrued customer billings
Other Receivables
Other receivables	6,124	6,261
Fuel tax credits
Other Receivables
Other receivables	69,585	434
Other
Other Receivables
Other receivables	$ 8,536	$ 8,573

Land, Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Land, Property and Equipment
Land, property and equipment, gross	$ 678,904	$ 664,087
Less accumulated depreciation	(354,992)	(313,519)
Total land, property and equipment, net	323,912	350,568
Capitalized software costs, net	30,400	29,300
Accumulated amortization on the capitalized software costs	26,300	22,500
Amortization expense related to the capitalized software costs	3,900	3,700	$ 4,400
Amount included in accounts payable balances	3,000	4,600
Land
Land, Property and Equipment
Land, property and equipment, gross	3,476	3,681
LNG liquefaction plants
Land, Property and Equipment
Land, property and equipment, gross	94,633	94,633
Station equipment
Land, Property and Equipment
Land, property and equipment, gross	324,431	319,119
Trailers
Land, Property and Equipment
Land, property and equipment, gross	79,477	75,901
Other equipment
Land, Property and Equipment
Land, property and equipment, gross	101,655	97,268
Construction in progress
Land, Property and Equipment
Land, property and equipment, gross	$ 75,232	$ 73,485

Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 02, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued alternative fuels incentives	$ 27,839		$ 6,923
Accrued employee benefits	2,276		2,248
Accrued interest	220		78
Accrued gas and equipment purchases	11,383		12,833
Accrued property and other taxes	3,732		3,397
Salaries and wages	9,105		8,609
Other	13,142		14,381
Total accrued liabilities	$ 67,697	$ 47,973	$ 48,469

Debt - Debt Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2013
Long-term debt
Principal Balances, Total debt	$ 89,094	$ 79,928
Principal Balances, amounts due within one year	(56,097)	(4,811)
Principal Balances, long-term debt	32,997	75,117
Unamortized Debt Financing Costs, Total debt	209	213
Unamortized Debt Financing Costs, amounts due within one year	(84)	(99)
Unamortized Debt Financing Costs, long-term	125	114
Balance, Net of Financing Costs, Total debt	88,885	79,715
Balance, Net of Financing Costs, amounts due within one year	(56,013)	(4,712)
Balance, Net of Financing Costs, long-term debt	32,872	75,003
Summary of aggregate maturities of debt obligations
2020	56,097
2021	6,340
2022	6,515
2023	11,500
2024	8,642
Principal Balances, Total debt	89,094	79,928
7.5% Notes
Long-term debt
Principal Balances, Total debt	50,000	50,000
Unamortized Debt Financing Costs, Total debt	17	58
Balance, Net of Financing Costs, Total debt	$ 49,983	$ 49,942
Interest rate (as a percent)	7.50%	7.50%	7.50%
Summary of aggregate maturities of debt obligations
2020	$ 50,000
Principal Balances, Total debt	50,000	$ 50,000
5.25% Notes
Long-term debt
Principal Balances, Total debt		28,904
Unamortized Debt Financing Costs, Total debt		155
Balance, Net of Financing Costs, Total debt		28,749
Summary of aggregate maturities of debt obligations
Principal Balances, Total debt		28,904
NG Advantage debt
Long-term debt
Principal Balances, Total debt	33,898
Unamortized Debt Financing Costs, Total debt	192
Balance, Net of Financing Costs, Total debt	33,706
Summary of aggregate maturities of debt obligations
2020	5,857
2021	6,092
2022	6,300
2023	11,407
2024	4,242
Principal Balances, Total debt	33,898
SG Facility
Long-term debt
Principal Balances, Total debt	4,400
Balance, Net of Financing Costs, Total debt	4,400
Summary of aggregate maturities of debt obligations
2024	4,400
Principal Balances, Total debt	4,400
Other debt
Long-term debt
Principal Balances, Total debt	796	1,024
Balance, Net of Financing Costs, Total debt	796	1,024
Summary of aggregate maturities of debt obligations
2020	240
2021	248
2022	215
2023	93
Principal Balances, Total debt	$ 796	$ 1,024

Debt - 7.5% Notes (Details) $ / shares in Units, $ in Thousands				1 Months Ended	12 Months Ended
	Dec. 04, 2018 USD ($)	Jun. 29, 2018 USD ($)	Feb. 09, 2017 USD ($)	Jun. 30, 2013 USD ($) D $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 17, 2017 USD ($)	Feb. 21, 2017 USD ($)	Aug. 27, 2013 USD ($)
Long-term debt
Aggregate principal amount						$ 89,094	$ 79,928
7.5% Notes
Long-term debt
Interest rate (as a percent)				7.50%		7.50%	7.50%
Debt issuance amount				$ 150,000
Conversion price of shares (in dollars per share) \| $ / shares				$ 15.80
Percentage of the trade price of common stock that the conversion price must be at premium for the Company to force conversion				40.00%
Number of days within 30 consecutive trading days in which the trade price of the entity's common stock must be at premium of the conversion price for the Company to force conversion \| D				20
Number of consecutive trading days used to determine the conversion obligation on the notes for the Company to force conversion \| D				30
Period during which the debt instrument principal balance is required to be paid following its issuance				7 years
Repayment in shares at maturity covenant, maximum number of shares (in shares) \| shares				13,993,630
Repurchased face amount during period	$ 50,000	$ 25,000
Repayments of debt		$ 500
Repayments of convertible debt	$ 50,500
Aggregate principal amount						$ 50,000	$ 50,000
7.5% Notes \| Green Energy Investment Holdings, LLC
Long-term debt
Principal amount transferred									$ 11,800	$ 5,000
Aggregate principal amount						32,900
7.5% Notes \| Mr. Pickens
Long-term debt
Principal amount transferred								$ 40,000
Repurchased face amount during period			$ 25,000
Repayments of convertible debt			$ 21,800
Gain (loss) on repurchase of debt instrument					$ 3,200
7.5% Notes \| Other Third Parties
Long-term debt
Aggregate principal amount						$ 17,100

Debt - Plains Credit Facility (Details) $ in Millions	Feb. 29, 2016 USD ($)
Plains Credit Facility
Long-term debt
Line of credit limit (up to)	$ 50.0

Debt - SG Credit and TOTAL Credit Support Agreement (Details) - USD ($) $ in Thousands	Jan. 02, 2019	Dec. 31, 2019	Dec. 31, 2018
Long-term debt
Outstanding amount		$ 89,094	$ 79,928
SG Facility
Long-term debt
Outstanding amount		4,400
SG Facility \| Société Générale
Long-term debt
Maximum borrowing capacity (up to)	$ 100,000
Commitment fee percentage	0.39%
Covenant for debt default	$ 20,000
Outstanding amount		$ 4,400
SG Facility \| Société Générale \| London Interbank Offered Rate (LIBOR)
Long-term debt
Basis spread on variable rate	1.30%
SG Facility \| Total Holdings USA Inc.
Long-term debt
Maximum borrowing capacity (up to)	$ 100,000
Interest rate per quarter	2.50%
Covenant for debt default	$ 20,000
SG Facility \| Total Holdings USA Inc. \| London Interbank Offered Rate (LIBOR)
Long-term debt
Basis spread on variable rate	1.00%

Debt - NG Advantage Debt and Financing Lease Obligations (Details) $ in Millions					1 Months Ended
	Jan. 17, 2019 USD ($) installment	Dec. 20, 2018 USD ($)	Mar. 01, 2018 USD ($) installment	Dec. 18, 2017 USD ($) installment	Oct. 31, 2019 USD ($)	Jan. 07, 2019	Jan. 24, 2017 USD ($) installment	Nov. 30, 2016 USD ($) installment	May 12, 2016 USD ($) installment
Compression Station
Long-term debt
Sale leaseback transaction, purchase price		$ 7.0
Sale leaseback transaction, term		5 years
Annual rate (as a percent)		12.00%
Sale leaseback transaction, monthly rental payments		$ 0.1
Sale leaseback transaction, rent expense		4.7
Sale leaseback transaction, rent expense, repayment of promissory note		$ 2.0
Compression Equipment
Long-term debt
Sale leaseback transaction, purchase price					$ 7.5
Proceeds from sale of equipment in sale-leaseback agreement					$ 5.3
Sale leaseback transaction, term					5 years
Annual rate (as a percent)					10.47%
Sale Leaseback Transaction, Security Deposit, Amount					$ 2.2
BoA \| BoA MLA
Long-term debt
Proceeds from sale of equipment in sale-leaseback agreement				$ 2.1
Sale leaseback transaction, term				5 years
Number of equal monthly installments \| installment				60
Annual rate (as a percent)				4.86%
First National \| First National MLA
Long-term debt
Net proceeds, financing activities			$ 6.3
Sale leaseback transaction, term			6 years
Number of equal monthly installments \| installment			72
First National \| Nations MLA
Long-term debt
Annual rate (as a percent)			9.28%
Nations Fund I, LLC \| Nations MLA
Long-term debt
Proceeds from sale of equipment in sale-leaseback agreement	$ 3.4
Sale leaseback transaction, term	4 years
Number of equal monthly installments \| installment	48
Annual rate (as a percent)						9.18%
NG Advantage debt \| 4.41% Term Loan \| Commerce Bank & Trust Company
Long-term debt
Debt issuance amount									$ 6.3
Number of monthly installments \| installment									84
Interest rate (as a percent)									4.41%
NG Advantage debt \| 5.0% Term Loan \| Commerce Bank & Trust Company
Long-term debt
Debt issuance amount							$ 6.2
Number of monthly installments \| installment							84
Interest rate (as a percent)							5.00%
NG Advantage debt \| 5.17% Term Loan \| Wintrust Commercial Finance
Long-term debt
Debt issuance amount								$ 4.7
Number of monthly installments \| installment								72
Interest rate (as a percent)								5.17%

Debt - Other Debt (Details) - Other debt	Dec. 31, 2019	Dec. 31, 2018
Long-term debt
Weighted average interest rate	4.78%	4.78%
Maximum
Long-term debt
Interest rate (as a percent)	5.02%

Stockholders' Equity - Authorized Shares (Details)	Dec. 31, 2019 class $ / shares shares	Dec. 31, 2018 $ / shares shares
Stockholders' Equity Note [Abstract]
Authorized number of classes of capital stock \| class	2
Common stock, par value (in dollars per share) \| $ / shares	$ 0.0001	$ 0.0001
Preferred stock, par value (in dollars per share) \| $ / shares	$ 0.0001	$ 0.0001
Authorized shares (in shares)	305,000,000
Common stock, authorized (in shares)	304,000,000	304,000,000
Preferred stock, authorized (in shares)	1,000,000	1,000,000

Stockholders' Equity - Voting Rights (Details)	Dec. 31, 2019 Vote
Equity [Abstract]
Number of votes per share held by holders of common stock	1

Stockholders' Equity - Issuance of Common Stock and Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Jun. 13, 2018	May 09, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 31, 2017
Private Placement
ATM Program Activity
Fees and issuance costs	$ 1,900
Number of shares issued in transaction (in shares)		50,856,296
Share price (in dollars per share)		$ 1.64
Percentage of ownership after transaction	25.00%
Consideration received	$ 83,400
Private Placement \| Purchase Percentage Covenant, Threshold
ATM Program Activity
Percentage of ownership after transaction		5.00%
Private Placement \| Purchase Percentage Covenant, Maximum
ATM Program Activity
Percentage of ownership after transaction		30.00%
Sales Agreement \| Citigroup
Stockholders' equity
Common stock, amount authorized (up to)						$ 200,000
ATM Program Activity
Gross proceeds					$ 10,767
Fees and issuance costs					311
Net proceeds					$ 10,456
Shares issued (in shares)					3,802,500
NG Advantage Warrants \| NG Advantage
ATM Program Activity
Fair value of warrants outstanding			$ 0	$ 1,100
Gain (loss) from the change in fair value			$ 1,000	$ (500)	$ 0
NG Advantage Warrants \| Common stock \| NG Advantage
Stockholders' equity
Number of shares that can be purchased upon exercise of warrants (in shares)			765,106

Stockholders' Equity - Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-based compensation
Stock-based compensation expense, net of $0 tax in 2016, 2017 and 2018	$ 3,880	$ 5,307	$ 8,423
Stock-based compensation expense, tax	$ 0	$ 0	$ 0
2016 Plan
Stock-based compensation
Number of shares available for future grant	2,054,993
2016 Plan \| Stock options
Stock-based compensation
Vesting period	3 years
Contractual term	10 years
Number of Shares
Outstanding at the beginning of the period (in shares)	8,699,677
Granted (in shares)	2,183,691
Exercised (in shares)	(58,602)
Forfeited or expired (in shares)	(1,703,101)
Outstanding at the end of the period (in shares)	9,121,665	8,699,677
Exercisable at the end of the period (in shares)	6,246,982
Vested and expected to vest at the end of the period (in shares)	9,121,665
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 8.06
Granted (in dollars per share)	2.19
Exercised (in dollars per share)	1.79
Forfeited or expired (in dollars per share)	10.07
Outstanding at the end of the period (in dollars per share)	6.32	$ 8.06
Exercisable at the end of the period (in dollars per share)	8.31
Vested and expected to vest at the end of the period (in dollars per share)	$ 6.32
Additional option disclosures
Outstanding at the end of the period, weighted average remaining contractual term	5 years 9 months 26 days
Exercisable at the end of the period, weighted average remaining contractual term	4 years 6 months 7 days
Vested and expected to vest at the end of the period, weighted average remaining contractual term	5 years 9 months 26 days
Outstanding at the end of the period, aggregate intrinsic value	$ 1,909
Exercisable at the end of the period, aggregate intrinsic value	812
Vested and expected to vest at the end of the period, aggregate intrinsic value	1,909
Total unrecognized compensation cost related to non-vested shares	$ 1,900
Weighted average period over which the total unrecognized compensation cost related to non-vested shares is expected to be recognized	1 year 5 months 12 days
Total fair value of shares vested	$ 1,600
Weighted-average assumption used for grants
Dividend yield	0.00%	0.00%	0.00%
Expected volatility			63.61%
Expected volatility, minimum	57.30%	70.20%
Expected volatility, maximum	61.50%	74.60%
Risk-free interest rate			2.05%
Risk-free interest rate, minimum	2.11%	2.70%
Risk-free interest rate, maximum	2.53%	2.71%
Expected life	6 years	6 years	6 years
Stock-based compensation
Weighted-average grant date fair values of options granted (in dollars per share)	$ 1.28	$ 0.88	$ 1.67
Exercised during the period, aggregate intrinsic value	$ 100	$ 0
Stock-based compensation expense	$ 2,200	$ 2,000	$ 2,200
2016 Plan \| Stock options \| Vesting over the first year
Stock-based compensation
Vesting percentage	34.00%
2016 Plan \| Stock options \| Vesting over the second year
Stock-based compensation
Vesting percentage	33.00%
2016 Plan \| Stock options \| Vesting over the third year
Stock-based compensation
Vesting percentage	33.00%
Asset impairments and other charges
Stock-based compensation
Stock-based compensation expense, net of $0 tax in 2016, 2017 and 2018			$ 300

Stockholders' Equity - Restricted Stock Units (Details) - Service-Based RSUs - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Outstanding at the beginning of the period (in shares)	2,279,601
Granted (in shares)	0
Vested (in shares)	(952,032)
Forfeited or expired (in shares)	(95,764)
Outstanding at the end of the period (in shares)	1,231,805	2,279,601
Weighted Average Fair Value at Grant Date
Outstanding at the beginning of the period (in dollars per share)	$ 1.88
Granted (in dollars per share)		$ 1.36	$ 1.36
Vested (in dollars per share)	2.13
Forfeited or expired (in dollars per share)	1.59
Outstanding at the end of the period (in dollars per share)	$ 1.71	$ 1.88
Total unrecognized compensation cost related to non-vested shares	$ 0.8
Weighted average period over which the total unrecognized compensation cost related to non-vested shares is expected to be recognized	10 months 28 days
Stock-based compensation expense	$ 1.5	$ 3.0	$ 5.9
Vesting over the first year
Weighted Average Fair Value at Grant Date
Vesting percentage	34.00%
Vesting over the second year
Weighted Average Fair Value at Grant Date
Vesting percentage	33.00%
Vesting over the third year
Weighted Average Fair Value at Grant Date
Vesting percentage	33.00%

Stockholders' Equity - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan $ in Millions		12 Months Ended			32 Months Ended
	May 07, 2013 period shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 shares
Stock-based compensation
Purchase price of shares expressed as percentage of fair market value of common stock	85.00%
Number of non-concurrent offering periods \| period	2
Number of shares reserved (in shares)	2,500,000
Stock-based compensation expense \| $		$ 0.0	$ 0.0	$ 0.0
Shares sold pursuant to the ESPP (in shares)					526,307

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of loss before income taxes
U.S.	$ 14,981	$ (9,153)	$ (44,535)
Foreign	(864)	311	(38,770)
Income (loss) before income taxes	14,117	(8,842)	(83,305)
Current:
Federal			31
State	116	341	231
Foreign	4		224
Total current	120	341	486
Deferred:
Federal	293		(978)
State	445		(184)
Foreign			(1,238)
Total deferred	738		(2,400)
Total tax expense (benefit)	$ 858	$ 341	(1,914)
Federal income tax benefit, utilization of operating loss carryforwards			6,900
State and local income tax benefit, utilization of operating loss carryforwards			$ 1,500
Federal income tax rate	21.00%	21.00%	35.00%
Reconciliation of the income tax provision
Computed expected tax (benefit)	$ 2,964	$ (1,857)	$ (29,157)
Nondeductible expenses	3,087	5,674	13,420
Tax rate differential on foreign earnings	245	(56)	11,860
Joint ventures	(369)	947
Noncontrolling interest	4,114	1,133
Impact of federal income tax rate change			59,729
Tax credits	(10,314)	(6,603)	(27)
Other	665	985	2,376
Change in valuation allowance	466	118	(60,115)
Total tax expense (benefit)	858	341	(1,914)
Tax benefit related to exclusion of AFTC	10,500	6,100	$ 0
Deferred tax assets:
Accrued expenses	4,899	5,254
Alternative minimum tax and general business credits	6,651	6,801
Stock option expense	9,254	11,210
Other	1,456	1,998
Loss carryforwards	107,722	106,957
Total deferred tax assets	129,982	132,220
Less valuation allowance	(122,147)	(120,801)
Net deferred tax assets	7,835	11,419
Deferred tax liabilities:
Commodity swap contracts	(998)	(2,751)
Depreciation and amortization	(911)	(2,672)
Goodwill	(1,910)	(1,650)
Investments in joint ventures and partnerships	(4,754)	(4,346)
Total deferred tax liabilities	(8,573)	$ (11,419)
Net deferred tax liabilities	$ (738)

Income Taxes - Tax Credit Carryforwards (Details) $ in Millions	Dec. 31, 2019 USD ($)
Federal
Income Taxes
Operating loss carryforwards	$ 430.2
Federal \| General
Income Taxes
Tax credit carryforwards	6.4
State
Income Taxes
Operating loss carryforwards	298.3
Foreign
Income Taxes
Operating loss carryforwards	$ 2.0

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation allowance
Deferred tax assets, valuation allowance	$ 122,147	$ 120,801
Net increase in valuation allowance	1,300	0
Reconciliation of the total amounts of unrecognized tax benefits
Unrecognized tax benefit at the beginning of the period	36,243	34,065
Gross increases—tax positions in current year	5,232	2,178
Unrecognized tax benefit at the end of the period	41,475	36,243	$ 34,065
Additional information on income tax
Accrued interest expense and penalties	0
Interest expense related to uncertain tax positions	$ 0	$ 0	$ 100

Commitments and Contingencies - Long-Term Take-or-Pay Natural Gas Purchase Contracts (Details) $ in Millions	Dec. 31, 2019 USD ($)
CNG supply agreement \| JTA
Fixed commitments under the contract payable in future
2020	$ 0.7
2021	0.2
2022	0.1
Natural Gas Supply Agreement \| DGS
Fixed commitments under the contract payable in future
2020	5.0
2021	1.2
2022	1.2
2023	$ 1.2

Commitments and Contingencies - Long-Term Natural Gas Purchase Contracts (Details) - Long-Term Natural Gas Purchase Contracts - USD ($) $ in Millions	1 Months Ended
	Jun. 30, 2017	Dec. 31, 2019
Other Commitments [Line Items]
Term of agreement	5 years
Nonrefundable amount	$ 13.4
Due in 2020		$ 5.1
Due in 2021		12.5
Due in 2022		$ 11.1

Leases - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Leases - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases
Sales-type lease, interest income	$ 0.1
Rent expense		$ 6.6
Weighted average interest rate		4.48%
Value of the equipment under capital lease		$ 6.1
Accumulated amortization		$ 1.8
Sales-type leases interest rate		13.50%
NG Advantage
Leases
Residual value of leased asset	1.4
Mr. Pickens
Leases
Lessee, operating lease, monthly rental payments	$ 0.1
Lessee, operating lease, monthly rental payments		$ 0.1	$ 0.1

Leases - Finance and Operating Lease Asset and Liability Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 02, 2019	Dec. 31, 2018
Finance leases:
Land, property and equipment, gross	$ 678,904		$ 664,087
Accumulated depreciation	(354,992)		(313,519)
Total land, property and equipment, net	323,912		350,568
Current portion of finance lease obligations	$ 615		693
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Current portion of finance lease obligations
Long-term portion of finance lease obligations	$ 2,715		3,776
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term portion of finance lease obligations
Total finance lease liabilities	$ 3,330
Operating leases:
Operating lease right-of-use assets	$ 28,627	$ 24,453
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Operating lease right-of-use assets
Current portion of operating lease obligations	$ 3,359
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Current portion of operating lease obligations
Long-term portion of operating lease obligations	$ 26,206
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term portion of operating lease obligations
Operating Lease, Liability, Total	$ 29,565	$ 25,943
Finance Leased Assets
Finance leases:
Land, property and equipment, gross	5,177
Accumulated depreciation	(2,134)
Total land, property and equipment, net	3,043
Land
Finance leases:
Land, property and equipment, gross	3,476		$ 3,681
Operating leases:
Operating lease right-of-use assets	17,978
Operating Lease, Liability, Total	17,978
LNG plant, office spaces and warehouses
Operating leases:
Operating lease right-of-use assets	10,624
Operating Lease, Liability, Total	11,562
Office equipment
Operating leases:
Operating lease right-of-use assets	25
Operating Lease, Liability, Total	$ 25

Leases - Components of Lease Expense (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Finance leases:
Depreciation on assets under finance leases	$ 498
Interest on lease liabilities	189
Total finance leases expense	687
Operating leases:
Lease expense	6,630
Lease expense on short-term leases	1,950
Variable lease expense	2,755
Sublease income	(206)
Total operating leases expense	$ 11,129

Leases - Supplemental Information (Details) $ in Thousands	12 Months Ended
Leases - Supplemental Information (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Leases
Operating cash outflows from finance leases	$ 189
Operating cash outflows from operating leases	5,350
Financing cash outflows from finance leases	1,667
Assets obtained in exchange for new finance lease liabilities	519
ROU assets obtained in exchange for new operating lease liabilities	$ 31,861
Weighted-average remaining lease term - finance leases	4 years 5 months 27 days
Weighted-average remaining lease term - operating leases	11 years 1 month 6 days
Weighted-average discount rate - finance leases	5.09%
Weighted-average discount rate - operating leases	8.29%

Leases - Maturities of Finance and Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 02, 2019
Finance Leases
2020	$ 767
2021	679
2022	560
2023	462
2024	1,026
Thereafter	314
Total minimum lease payments	3,808
Less amount representing interest	(478)
Present value of lease liabilities	3,330
Operating Leases
2020	5,484
2021	4,658
2022	3,736
2023	3,712
2024	3,704
Thereafter	25,208
Total minimum lease payments	46,502
Less amount representing interest	(16,937)
Operating lease obligations	$ 29,565	$ 25,943

Leases - Maturities of Lease Receivables (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Fiscal year:
2020	$ 186
2021	186
2022	186
2023	186
2024	186
Thereafter	1,054
Total minimum lease payments	1,984
Less amount representing interest	(935)
Present value of lease receivables	$ 1,049

Leases - Operating Lease Commitments (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Fiscal year:
2019	$ 6,340
2020	4,332
2021	3,311
2022	2,409
2023	2,300
Thereafter	13,214
Total future minimum lease payments	$ 31,906

Leases - Capitalized Lease Obligation (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Future payments under these capital leases
2019	$ 883
2020	742
2021	656
2022	540
2023	529
Thereafter	1,868
Total minimum lease payments	5,218
Less amount representing interest	(749)
Capital lease obligations	4,469
Less current portion	(693)
Capital lease obligations, less current portion	$ 3,776

Leases - Capitalized Lease Receivables (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Future receipts under the leases
2019	$ 186
2020	186
2021	186
2022	186
2023	186
Thereafter	1,240
Total	2,170
Less amount representing interest	(1,080)
Present value of future minimum lease receipts	$ 1,090

401(k) Plan (Details) - USD ($) $ in Millions	12 Months Ended
401(k) Plan (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Maximum percentage of base pay that can be contributed by employees through salary deferrals	90.00%
Contribution by the company	$ 1.3	$ 1.3	$ 1.3

Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income (loss)	$ 20,421	$ (3,790)	$ (79,237)
Weighted average common shares outstanding	204,573,287	180,655,435	150,430,239
Dilutive effect of potential common shares from restricted stock units and stock options	1,414,222
Weighted average common shares outstanding - diluted	205,987,509	180,655,435	150,430,239
Basic (in dollars per share)	$ 0.10	$ (0.02)	$ (0.53)
Diluted (in dollars per share)	$ 0.10	$ (0.02)	$ (0.53)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Income (Loss) Per Share - Anti-dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock options
Net Loss Per Share
Anti-dilutive securities (in shares)	7,652,463.00	8,699,677.00	8,613,854.00
Convertibles notes
Net Loss Per Share
Anti-dilutive securities (in shares)	3,164,557.00	3,164,557.00	14,991,521.00
Restricted stock units
Net Loss Per Share
Anti-dilutive securities (in shares)		2,279,601.00	1,832,575.00

Related Party Transactions (Details) $ in Millions	12 Months Ended
Related Party Transactions (Details) $ in Millions	Dec. 31, 2019 USD ($)
Related Party Transactions [Abstract]
Proceeds for related party	$ 1.7
Related party expense	$ 0.9

Reportable Segments and Geographic Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Geographic Information
Total revenue	$ 344,065	$ 346,419	$ 341,599
Total operating income (loss)	9,928	3,895	(134,447)
Total long-lived assets	415,774	443,182	465,618
United States
Geographic Information
Total revenue	338,549	337,531	316,756
Total operating income (loss)	10,805	3,548	(96,228)
Total long-lived assets	415,548	442,897	465,245
Canada
Geographic Information
Total revenue	5,516	8,888	6,846
Total operating income (loss)	(877)	347	(9,495)
Total long-lived assets	$ 226	$ 285	373
Other
Geographic Information
Total revenue			17,997
Total operating income (loss)			$ (28,724)

Concentrations (Details) - Natural gas expense - Supplier concentration	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Top Two Customers
Supplier Concentrations
Concentration risk, percentage		10.00%	10.00%
Top Three Customers
Supplier Concentrations
Concentration risk, percentage	10.00%

Subsequent Events (Details) - NG Advantage			1 Months Ended	12 Months Ended
Subsequent Events (Details) - NG Advantage	Oct. 01, 2018	Feb. 28, 2018	Feb. 29, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Percentage of ownership after transaction	61.70%	53.50%		64.60%
Subsequent Event
Subsequent Event [Line Items]
Percentage of ownership after transaction			93.20%

Schedule II: Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowances for Doubtful Trade Receivables
Movement in valuation and qualifying accounts
Balance at the beginning of the period	$ 1,919	$ 1,276	$ 1,063
Charges (benefit) to operations	908	1,169	395
Deductions	(415)	(526)	(182)
Balance at the end of the period	2,412	1,919	1,276
Allowance for Doubtful Notes Receivables
Movement in valuation and qualifying accounts
Balance at the beginning of the period	4,163	4,544	1,230
Charges (benefit) to operations	931	0	3,344
Deductions	(1,763)	(381)	(30)
Balance at the end of the period	$ 3,331	$ 4,163	$ 4,544

Fair Value Measurements - Commodity Swap Contracts (Details) - Not Designated as Hedging Instrument - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Commodity swap contracts \| Minimum \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.76	1.71
Commodity swap contracts \| Minimum \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.79	0.76
Commodity swap contracts \| Minimum \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.32	1.22
Commodity swap contracts \| Maximum \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.88	1.79
Commodity swap contracts \| Maximum \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.16	1.16
Commodity swap contracts \| Maximum \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	2.30	2.12
Commodity swap contracts \| Weighted Average \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.81	1.75
Commodity swap contracts \| Weighted Average \| Historical Differential to PADD 3 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.91	0.89
Commodity swap contracts \| Weighted Average \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.78	1.55
Fueling agreements \| Minimum \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.76
Fueling agreements \| Minimum \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.32
Fueling agreements \| Maximum \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.88
Fueling agreements \| Maximum \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	2.30
Fueling agreements \| Weighted Average \| ULSD Gulf Coast Forward Curve
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.81
Fueling agreements \| Weighted Average \| Historical Differential to PADD 5 Diesel
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	1.78