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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2016	May 01, 2016
Document and Entity Information
Entity Registrant Name	Clean Energy Fuels Corp.
Entity Central Index Key	0001368265
Document Type	10-Q
Document Period End Date	Mar. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		105,397,670
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q1

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 87,239	$ 43,724
Restricted cash	8,775	4,240
Short-term investments	75,696	102,944
Accounts receivable, net of allowance for doubtful accounts of $1,895 and $2,038 as of December 31, 2015 and March 31, 2016, respectively	71,898	73,645
Other receivables	26,045	60,667
Inventory	30,037	29,289
Prepaid expenses and other current assets	14,194	14,657
Total current assets	313,884	329,166
Land, property and equipment, net	505,940	516,324
Notes receivable and other long-term assets, net	17,415	14,732
Investments in other entities	5,621	5,695
Goodwill	94,207	91,967
Intangible assets, net	43,579	42,644
Total assets	980,646	1,000,528
Current liabilities:
Current portion of debt and capital lease obligations	139,991	149,856
Accounts payable	21,717	26,906
Accrued liabilities	55,828	59,082
Deferred revenue	9,325	10,549
Total current liabilities	226,861	246,393
Long-term portion of debt and capital lease obligations	319,495	352,294
Long-term debt, related party	65,000	65,000
Other long-term liabilities	8,077	7,896
Total liabilities	619,433	671,583
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value. Authorized 1,000,000 shares; issued and outstanding no shares	0	0
Common stock, $0.0001 par value. Authorized 224,000,000 shares; issued and outstanding 92,382,717 shares and 100,237,328 shares at December 31, 2015 and March 31, 2016, respectively	10	9
Additional paid-in capital	938,990	915,199
Accumulated deficit	(588,855)	(591,683)
Accumulated other comprehensive loss	(15,026)	(20,973)
Total Clean Energy Fuels Corp. stockholders’ equity	335,119	302,552
Noncontrolling interest in subsidiary	26,094	26,393
Total stockholders’ equity	361,213	328,945
Total liabilities and stockholders’ equity	$ 980,646	$ 1,000,528

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 2,038	$ 1,985
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized shares	1,000,000	1,000,000
Preferred stock, issued shares	0	0
Preferred stock, outstanding shares	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized shares	224,000,000	224,000,000
Common stock, issued shares	100,237,328	92,382,717
Common stock, outstanding shares	100,237,328	92,382,717

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenue:
Product revenues	$ 83,992	$ 69,297
Service revenues	11,790	16,551
Total revenues	95,782	85,848
Cost of sales (exclusive of depreciation and amortization shown separately below):
Product cost of sales	53,371	55,379
Service cost of sales	5,884	9,354
Loss (gain) from change in fair value of derivative warrants	2	(883)
Selling, general and administrative	25,593	30,233
Depreciation and amortization	14,961	12,886
Total operating expenses	99,811	106,969
Operating income (loss)	(4,029)	(21,121)
Gain from extinguishment of debt	(15,923)	0
Interest expense, net	(9,160)	(9,895)
Other income (expense), net	250	547
Loss from equity method investments	(74)	(204)
Income (loss) before income taxes	2,910	(30,673)
Income tax (expense) benefit	(381)	(854)
Net income (loss)	2,529	(31,527)
Loss from noncontrolling interest	299	380
Net income (loss) attributable to Clean Energy Fuels Corp.	$ 2,828	$ (31,147)
Income (loss) per share attributable to Clean Energy Fuels Corp.:
Basic (in dollars per share)	$ 0.03	$ (0.34)
Diluted (in dollars per share)	$ 0.03	$ (0.34)
Weighted-average common shares outstanding:
Basic (in shares)	97,178,768	91,317,053
Diluted weighted average number of common shares outstanding	99,821,844	91,317,053

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net income (loss)	$ 2,529	$ (31,527)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in 2015 and 2016	6,515	(5,681)
Foreign currency adjustments on intra-entity long-term investments, net of $0 tax in 2015 and 2016	(635)	(3,311)
Unrealized losses on available-for-sale securities, net of $0 tax in 2015 and 2016	67	16
Total other comprehensive income (loss), net of tax	5,947	(8,976)
Comprehensive loss	8,476	(40,503)
Clean Energy Fuels Corp.
Net income (loss)	2,828	(31,147)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in 2015 and 2016	6,515	(5,681)
Foreign currency adjustments on intra-entity long-term investments, net of $0 tax in 2015 and 2016	(635)	(3,311)
Unrealized losses on available-for-sale securities, net of $0 tax in 2015 and 2016	67	16
Total other comprehensive income (loss), net of tax	5,947	(8,976)
Comprehensive loss	8,775	(40,123)
Noncontrolling Interest
Net income (loss)	(299)	(380)
Other comprehensive income (loss), net of tax:
Comprehensive loss	$ (299)	$ (380)

Condensed Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustments, tax	$ 0	$ 0
Foreign currency adjustments on intra-entity long-term investments, tax	0	0
Unrealized (losses) gains on available-for-sale securities, tax	$ 0	$ 0

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income (loss)	$ 2,529	$ (31,527)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	14,961	12,886
Provision for doubtful accounts, notes and inventory	665	110
Stock-based compensation expense	2,419	2,690
Gain from extinguishment of debt	(15,923)	0
Amortization of debt issuance cost	467	760
Changes in operating assets and liabilities, net of assets and liabilities acquired and disposed of:
Accounts and other receivables	35,935	35,565
Inventory	(748)	1,880
Prepaid expenses and other assets	(794)	4,541
Restricted cash	5,122	0
Accounts payable	(3,483)	(2,976)
Accrued expenses and other	(4,139)	(3,073)
Net cash used provided by (used in) operating activities	26,767	20,856
Cash flows from investing activities:
Purchases of short-term investments	(39,783)	(38,416)
Maturities and sales of short-term investments	66,894	47,006
Purchases and deposits on property and equipment	(5,246)	(12,506)
Loans made to customers	(849)	(1,675)
Payments on and proceeds from sales of loans receivable	234	623
Restricted cash	587	1,027
Net cash provided by (used in) investing activities	21,837	(3,941)
Cash flows from financing activities:
Issuances of common stock, net of taxes and fees paid	21,372	334
Proceeds from debt instruments	306	6
Proceeds from revolving line of credit	50,003	23
Repayment of borrowing under revolving line of credit	(4)	(24)
Repayment of capital lease obligations and debt instruments	(77,892)	(1,486)
Net cash provided by (used in) financing activities	(6,215)	(1,147)
Effect of exchange rates on cash and cash equivalents	1,126	(1,286)
Effect of exchange rates on cash and cash equivalents	43,515	14,482
Cash and cash equivalents, beginning of period	43,724	92,381
Cash and cash equivalents, end of period	87,239	106,863
Supplemental disclosure of cash flow information:
Income taxes paid	196	180
Interest paid, net of approximately $268 and $135 capitalized, respectively	$ 6,505	$ 5,941

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Cash Flows [Abstract]
Interest paid, capitalized	$ 0	$ 268

General	3 Months Ended
General	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
General	General Nature of Business: 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 otherwise) is engaged in the business of selling natural gas fueling solutions to its customers, primarily in the United States and Canada. The Company's principal business is supplying compressed natural gas (“CNG”), liquefied natural gas (“LNG”) and renewable natural gas (“RNG”) for light, medium and heavy-duty vehicles and providing operation, repair and maintenance ("O&M") services for vehicle fleet customer stations. As a comprehensive solution provider, the Company also designs, builds, operates, services, repairs and maintains fueling stations, manufactures, sells and services non-lubricated 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 to large industrial and institutional energy users who do not have direct access to natural gas pipelines, processes and sells RNG, sells tradable credits generated by selling natural gas and RNG as a vehicle fuel, including credits generated under the California and the Oregon Low Carbon Fuel Standards (collectively, "LCFS Credits") and Renewable Identification Numbers ("RIN Credits" or "RINs") generated under the federal Renewable Fuel Standard Phase 2, helps its customers acquire and finance natural gas vehicles and obtains federal, state and local tax credits, grants and incentives. Basis of Presentation: The accompanying interim unaudited condensed 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 financial position, results of operations, comprehensive loss and cash flows as of and for the three months ended March 31, 2015 and 2016. All intercompany accounts and transactions have been eliminated in consolidation. The three month periods ended March 31, 2015 and 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any future year. Certain information and disclosures normally included in the notes to the financial statements have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”), but the resultant disclosures contained herein are in accordance with accounting principles generally accepted in the United States of America (“US GAAP”) as they apply to interim reporting. The condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the year ended December 31, 2015 that are included in the Company’s Annual Report on Form 10-K filed with the SEC on March 3, 2016. During the three months ended March 31, 2016, the Company adopted Accounting Standards Update (ASU) No. 2015-03, Interest - Imputation of Interest, which requires that debt issuance costs be presented in the balance sheet as a deduction from the carrying amount of the related liability, rather than as a deferred charge. The standard is required to be applied on a retrospective basis. As a result of applying the standard, unamortized debt issuance costs of $273 were reclassed from Prepaid expenses and other current assets to Current portion of long-term debt and capital lease obligations and $4,991 were reclassed from Notes receivable and other long-term assets to Long-term debt and capital lease obligations as of March 31, 2015. Use of Estimates: The preparation of condensed consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and revenues and expenses recorded during the reporting period. Actual results could differ from those estimates. Significant estimates made in preparing the condensed consolidated financial statements include (but are not limited to) those related to revenue recognition, goodwill and long-lived intangible asset valuations and impairment assessments, income tax valuations, and stock-based compensation expense. Revenue Recognition: Effective January 1, 2016, the Company implemented a cost tracking system that provides for a detailed tracking of costs incurred on its station construction projects on a project by project basis. As a result of implementing this tracking system, the Company is able to make reliable estimates as to the percentage that a project is complete at the end of each reporting period. Beginning January 1, 2016, the Company began using the percentage of completion method to recognize revenue for station construction projects using the cost-to-cost method. Under this method, the Company estimates the percentage of completion based on the costs incurred to date for each contract in comparison to the estimated total costs for such contract at completion. The Company historically recognized revenue on station construction projects using the completed-contract method because it did not have a reliable means to make estimates of the percentage of the contract completed. Under the completed contract method, the construction projects were considered substantially complete at the earlier of customer acceptance of the fueling station or the time when the fuel dispensing activities began. The sale of compressors and related equipment continue to be recognized under the percentage of completion method as in previous periods. Station construction contracts are generally short-term with an exception for larger more complex stations, which can take up to 24 months to complete. Management evaluates the performance of contracts on an individual contract basis. Contract price and cost estimates are reviewed periodically as work progresses and adjustments proportionate to the percentage of completion are reflected in contract revenues in the reporting period when such estimates are revised. The nature of accounting for contracts is such that refinements of the estimating process for changing conditions and new developments are continuous and characteristic of the process. Many factors can and do change during a contract performance period which can result in a change to contract profitability including differing site conditions, the availability of skilled contract labor, the performance of major suppliers and subcontractors, and unexpected changes in material costs. These factors may result in revision to costs and income and are recognized in the period in which the revisions become known. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses become known. During the three months ended March 31, 2016, there were no losses on open contracts. The Company considers unapproved change orders to be contract variations for which the customer has approved the change of scope but the associated price change has not yet been agreed upon. Change orders that are unapproved as to both price and scope are evaluated as claims. Warranty claims have historically been insignificant. There were no significant unapproved change orders, claims, contract penalties, settlements or changes in contract estimates during the three months ended March 31, 2016. As a result of using the percentage of completion method to recognize revenues, station construction project sales during the three months ended March 31, 2016 provided $9,393 in revenues, $1,100 in operating income, and $0.01 of income per diluted share amounts for such period that would otherwise not have been recognized during such period under the completed contract method.

Investments in Other Entities and Noncontrolling Interest in a Subsidiary	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Acquisition and Divestitures	Mansfield On September 16, 2014, the Company formed a joint venture with Mansfield Ventures LLC (“Mansfield”) called Mansfield Clean Energy Partners LLC (“MCEP”), which is designed to provide natural gas fueling solutions to bulk fuel haulers in the U.S. The Company and Mansfield each have a 50% ownership interest in MCEP. The Company accounts for its interest using the equity method of accounting, as the Company has the ability to exercise significant influence over MCEP’s operations. The Company recorded a loss from this investment of $204 and $74 for the three months ended March 31, 2015 and March 31, 2016, respectively, and has an investment balance of $4,695 and $4,621 at December 31, 2015 and March 31, 2016, respectively. NG Advantage On October 14, 2014, the Company entered into a Common Unit Purchase Agreement (“UPA”) with NG Advantage, LLC (“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 large industrial and institutional energy users, such as hospitals, food processors, manufacturers and paper mills, which do not have direct access to natural gas pipelines. The Company viewed the acquisition as a strategic investment in the expansion of the Company’s initiative to deliver natural gas to industrial and institutional energy users .The results of NG Advantage’s operations have been included in the Company’s consolidated financial statements since October 14, 2014. The Company reported a loss from this noncontrolling interest of $380 and $299 for the three months ended March 31, 2015 and March 31, 2016, respectively. The noncontrolling interest was $26,393 and $26,094 at December 31, 2015 and March 31, 2016, respectively.

Cash and Cash Equivalents	3 Months Ended
Cash and Cash Equivalents	Mar. 31, 2016
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents 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”), Canadian Deposit Insurance Corporation (“CDIC,”) and other foreign insurance limits. Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash deposits. The amounts in excess of FDIC, CDIC and other foreign insurance limits were approximately $40,691 and $84,841 as of December 31, 2015 and March 31, 2016, respectively.

- Definition

The entire disclosure for cash and cash equivalent footnotes, which may include the types of deposits and money market instruments, applicable carrying amounts, restricted amounts and compensating balance arrangements. Cash and equivalents include: (1) currency on hand (2) demand deposits with banks or financial institutions (3) other kinds of accounts that have the general characteristics of demand deposits (4) short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments maturing within three months from the date of acquisition qualify.

+ References + Details

Restricted Cash

3 Months Ended

Mar. 31, 2016

Restricted Cash.

Restricted Cash

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. Restricted cash consisted of the following as of December 31, 2015 and March 31, 2016:



	December 31, 2015		March 31, 2016
Short-term restricted cash:
Standby letters of credit	$	1,631	$	6,753
Canton Bonds (see Note 10)	2,609		2,022
Total short-term restricted cash	$	4,240	$	8,775

Investments

3 Months Ended

Mar. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Investments

Available-for-sale investments are carried at fair value, inclusive of unrealized gains and losses. Unrealized gains and losses are included in other comprehensive income (loss) net of applicable income taxes. Gains or losses on sales of available-for-sale investments are recognized on the specific identification basis. All of the Company’s short-term investments are classified as available-for-sale securities.

The Company reviews available-for-sale investments 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 March 31, 2016, the Company believes its carrying values for its available-for-sale investments are properly recorded.

Short-term investments as of December 31, 2015 are summarized as follows:



	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value
Municipal bonds & notes	$	16,797	$	(7	)	$	16,790
Zero coupon bonds	500		(1		)	499
Corporate bonds	37,181		(77		)	37,104
Certificate of deposits	48,551		—			48,551
	$	103,029	$	(85	)	$	102,944

Short-term investments as of March 31, 2016 are summarized as follows:



	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value
Municipal bonds & notes	$	11,558	$	(9	)	$	11,549
Zero coupon bonds	1,000		—			1,000
U.S. government agencies	5,000		2			$	5,002
Corporate bonds	9,548		(3		)	9,545
Certificate of deposits	48,600		—			48,600
	$	75,706	$	(10	)	$	75,696

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Other Receivables

3 Months Ended

Mar. 31, 2016

Receivables [Abstract]

Other Receivables

Other receivables at December 31, 2015 and March 31, 2016 consisted of the following:



	December 31, 2015		March 31, 2016
Loans to customers to finance vehicle purchases	$	10,531	$	9,532
Accrued customer billings	7,106		7,610
Fuel tax and carbon credits	40,730		6,173
Other	2,300		2,730
	$	60,667	$	26,045

Inventory

3 Months Ended

Mar. 31, 2016

Inventory Disclosure [Abstract]

Inventories

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 market. The Company writes down the carrying value of its inventory to net realizable value for estimated obsolescence or unmarketable inventory in an amount equal to the difference between the cost of inventory and its estimated realizable value based upon assumptions about future demand and market conditions, among other factors.

Inventories consisted of the following as of December 31, 2015 and March 31, 2016:



	December 31, 2015		March 31, 2016
Raw materials and spare parts	$	25,113	$	26,127
Work in process	973		2,742
Finished goods	3,203		1,168
	$	29,289	$	30,037

Land, Property and Equipment

3 Months Ended

Mar. 31, 2016

Property, Plant and Equipment [Abstract]

Land, Property and Equipment

Land, property and equipment at December 31, 2015 and March 31, 2016 are summarized as follows:



	December 31, 2015			March 31, 2016
Land	$	2,858		$	2,858
LNG liquefaction plants	94,634			94,634
RNG plants	46,397			46,397
Station equipment	316,258			317,387
Trailers	50,414			50,414
Other equipment	83,687			86,739
Construction in progress	139,586			139,099
	733,834			737,528
Less: accumulated depreciation	(217,510		)	(231,588		)
	$	516,324		$	505,940

Included in land, property and equipment are capitalized software costs of $22,886 and $23,384 as of December 31, 2015 and March 31, 2016, respectively. The accumulated amortization on the capitalized software costs is $13,793 and $14,731 as of December 31, 2015 and March 31, 2016, respectively. The Company recorded $716 and $938 of amortization expense related to the capitalized software costs during the three months ended March 31, 2015 and March 31, 2016, respectively.

As of March 31, 2015 and March 31, 2016, $13,771 and $6,077, respectively, are included in accounts payable and accrued liabilities balances, which amounts are related to purchases of property and equipment. These amounts are excluded from the condensed consolidated statements of cash flows as they are non-cash investing activities.

Accrued Liabilities

3 Months Ended

Mar. 31, 2016

Payables and Accruals [Abstract]

Accrued Liabilities

Accrued liabilities at December 31, 2015 and March 31, 2016 consisted of the following:



	December 31, 2015		March 31, 2016
Salaries and wages	$	9,537	$	5,328
Accrued gas and equipment purchases	14,133		10,716
Accrued property and other taxes	5,344		4,038
Accrued professional fees	1,105		874
Accrued employee benefits	3,042		3,242
Accrued warranty liability	1,826		1,791
Accrued interest	3,718		5,995
Other	20,377		23,844
	$	59,082	$	55,828

Debt

3 Months Ended

Mar. 31, 2016

Debt Disclosure [Abstract]

Debt

ebt

Debt and capital lease obligations at December 31, 2015 and March 31, 2016 consisted of the following and are further discussed below:



	December 31, 2015
	Principal Balances			Unamortized Debt Financing Costs			Balance, Net of Financing Costs
7.5% Notes(1)	$	150,000		399			149,601
SLG Notes	145,000			38			144,962
5.25% Notes	250,000			3,985			246,015
Canton Bonds	10,910			514			10,396
Capital lease obligations	6,448			—			6,448
Other debt	10,056			328			9,728
Total debt and capital lease obligations	572,414			5,264			567,150
Less amounts due within one year	(150,129		)	(273		)	(149,856		)
Total long-term debt and capital lease obligations	$	422,285		$	4,991		$	417,294



	March 31, 2016
	Principal Balances			Unamortized Debt Financing Costs			Balance Net of Financing Costs
7.5% Notes(1)	150,000			367			$	149,633
SLG Notes	85,000			14			84,986
5.25% Notes	217,500			3,129			214,371
PlainsCapital Bank Credit Facility	50,000			—			50,000
Canton Bonds	10,221			487			9,734
Capital lease obligations	6,437			—			6,437
Other debt	9,613			307			9,306
Total debt and capital lease obligations	528,771			4,304			524,467
Less amounts due within one year	(139,748		)	(243		)	(139,991		)
Total long-term debt and capital lease obligations	$	389,023		$	4,061		384,476

(1) Included in the 7.5% Notes is $65,000 in principal amount held by T. Boone Pickens, which are classified as “Long-term debt, related party” on the condensed consolidated balance sheet. See below for additional information.

7.5% Notes

On July 11, 2011, the Company entered into a loan agreement (the “CHK Agreement”) with Chesapeake NG Ventures Corporation (“Chesapeake”), an indirect wholly owned subsidiary of Chesapeake Energy Corporation, whereby Chesapeake agreed to purchase from the Company up to $150,000 of debt securities (the “CHK Financing”) pursuant to the issuance of three convertible promissory notes over a three-year period, each having a principal amount of $50,000 (each a “CHK Note” and collectively the “CHK Notes” and, together with the CHK Agreement and other transaction documents, the “CHK Loan Documents”). The first CHK Note was issued on July 11, 2011 and the second CHK Note was issued on July 10, 2012.

On June 14, 2013 (the “Transfer Date”), Boone Pickens and Green Energy Investment Holdings, LLC, an affiliate of Leonard Green & Partners, L.P. (collectively, the “Buyers”), and Chesapeake entered into a note purchase agreement (“Note Purchase Agreement”) pursuant to which Chesapeake sold the outstanding CHK Notes (the “Sale”) to the Buyers. Chesapeake assigned to the Buyers all of its right, title and interest under the CHK Loan Documents (the “Assignment”), and each Buyer severally assumed all of the obligations of Chesapeake under the CHK Loan Documents arising after the Sale and the Assignment including, without limitation, the obligation to advance an additional $50,000 to the Company in June 2013 (the “Assumption”). The Company also entered into the Note Purchase Agreement for the purpose of consenting to the Sale, the Assignment and the Assumption.

Contemporaneously with the execution of the Note Purchase Agreement, the Company entered into a loan agreement with each Buyer (collectively, the “Amended Agreements”). The Amended Agreements have the same terms as the CHK Agreement, other than changes to reflect the new ownership of the CHK Notes. Immediately following execution of the Amended Agreements, the Buyers delivered $50,000 to the Company in satisfaction of the funding requirement they had assumed from Chesapeake (the “June Advance”). In addition, the Company canceled the existing CHK Notes and re-issued replacement notes, and the Company also issued notes to the Buyers in exchange for the June Advance (the re-issued replacement notes and the notes issued in exchange for the June Advance are referred to herein as the “7.5% Notes”).

The 7.5% Notes have the same terms as the original CHK Notes, other than the changes to reflect their different holders. They 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, the holders of the 7.5% Notes have the right to exchange all or any portion of the principal and accrued and unpaid interest under each such note 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, following the second anniversary of the issuance of a 7.5% Note, 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 date and the Company may repay each 7.5% Note in shares of its common stock 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 Amended Agreements restrict the use of the proceeds of the 7.5% Notes to financing the development, construction and operation of LNG stations and payment of certain related expenses. The Amended Agreements also provide for 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 March 31, 2016.

On August 27, 2013, Green Energy Investment Holdings, LLC transferred $5,000 in principal amount of its 7.5% Notes to certain third parties.

As a result of the foregoing transactions, (i) Boone Pickens holds 7.5% Notes in the aggregate principal amount of $65,000, which 7.5% Notes are convertible into approximately 4,113,924 shares of the Company’s common stock at the 7.5% Notes Conversion Price, (ii) Green Energy Investment Holdings, LLC holds 7.5% Notes in the aggregate principal amount of $80,000, which 7.5% Notes are convertible into approximately 5,063,291 shares of the Company’s common stock at the 7.5% Notes Conversion Price, and (iii) other third parties hold 7.5% Notes in the aggregate principal amount of $5,000, which 7.5% Notes are convertible into approximately 316,456 shares of the Company's common stock at the 7.5% Notes Conversion Price.

SLG Notes

On August 24, 2011, the Company entered into convertible note purchase agreements (each, an “SLG Agreement” and collectively the “SLG Agreements”) with each of Springleaf Investments Pte. Ltd., a wholly-owned subsidiary of Temasek Holdings Pte. Ltd., Lionfish Investments Pte. Ltd., an investment vehicle managed by Seatown Holdings International Pte. Ltd., and Greenwich Asset Holding Ltd., a wholly-owned subsidiary of RRJ Capital Master Fund I, L.P. (each, a “Purchaser” and collectively, the “Purchasers”), whereby the Purchasers agreed to purchase from the Company $150,000 of 7.5% convertible promissory notes due in August 2016 (each a “SLG Note” and collectively the “SLG Notes”). The transaction closed and the SLG Notes were issued on August 30, 2011. On March 1, 2012, Springleaf Investments Pte. LTD transferred $24,000 in principal amount of the SLG Notes to Baytree Investments (Mauritius) Pte. Ltd.

The SLG Notes bear interest at the rate of 7.5% per annum and are convertible at the option of each Purchaser into shares of the Company’s common stock at a conversion price of $15.00 per share (the “SLG Conversion Price”). Upon written notice to the Company, the holders of the SLG Notes have the right to exchange all or any portion of the principal and accrued and unpaid interest under each such note for shares of the Company’s common stock at the SLG Conversion Price. Additionally, subject to certain restrictions, the Company can force conversion of each SLG Note into shares of its common stock if, following the second anniversary of the issuance of the SLG Notes, such shares trade at a 40% premium to the SLG Conversion Price for at least 20 trading days in any consecutive 30 trading day period. The entire principal balance of each SLG Note is due and payable five years following its issuance and the Company may repay the principal balance of each SLG Note in shares of its common stock or cash. All of the shares issuable upon conversion of the SLG 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 SLG Agreements also provide for customary events of default which, if any of them occurs, would permit or require the principal of, and accrued interest on, the SLG Notes to become, or to be declared, due and payable. No events of default under the SLG Notes had occurred as of March 31, 2016.

In April 2012, $1,003 of principal and accrued interest under an SLG Note was converted by the holder thereof into 66,888 shares of the Company’s common stock. In January and February 2013, $4,030 of principal and accrued interest under an SLG Note was converted by the holder thereof into 268,664 shares of the Company’s common stock.

On March 1, 2016, the Company repaid $60,000 in cash of the $145,000 outstanding principal amount and $1,812 in cash of accrued interest of the SLG Notes.

5.25% Notes

In September 2013, the Company completed a private offering of $250,000 in principal amount of 5.25% Convertible Senior Notes due 2018 (the “5.25% Notes”) and entered into an indenture governing the 5.25% Notes (the “Indenture”).

The net proceeds from the sale of the 5.25% Notes after the payment of certain debt issuance costs of $7,805 were $242,195. The Company has used, and intends to continue to use, the net proceeds from the sale of the 5.25% Notes to fund capital expenditures and for general corporate purposes.

The 5.25% Notes bear interest at a rate of 5.25% per annum, payable semi-annually in arrears on October 1 and April 1 of each year, beginning on April 1, 2014. The 5.25% Notes will mature on October 1, 2018, unless purchased, redeemed or converted prior to such date in accordance with their terms and the terms of the Indenture.

Holders may convert their 5.25% Notes, at their option, at any time prior to the close of business on the business day immediately preceding the maturity date of the 5.25% Notes. Upon conversion, the Company will deliver a number of shares of its common stock, per $1 principal amount of 5.25% Notes, equal to the conversion rate then in effect (together with a cash payment in lieu of any fractional shares). The initial conversion rate for the 5.25% Notes is 64.1026 shares of the Company’s common stock per $1 principal amount of Notes (which is equivalent to an initial conversion price of approximately $15.60 per share of the Company’s common stock). The conversion rate is subject to adjustment upon the occurrence of certain specified events as described in the Indenture. Upon the occurrence of certain corporate events prior to the maturity date of the 5.25% Notes, the Company will, in certain circumstances, in addition to delivering the number of shares of the Company’s common stock deliverable upon conversion of the 5.25% Notes based on the conversion rate then in effect (together with a cash payment in lieu of any fractional shares), pay holders that convert their 5.25% Notes a cash make-whole payment in an amount as calculated in accordance with the Indenture. The Company may, at its option, irrevocably elect to settle its obligation to pay any such make-whole payment in shares of its common stock instead of in cash. The amount of any make-whole payment, whether it is settled in cash or in shares of the Company’s common stock upon the Company’s election, will be determined based on the date on which the corporate event occurs or becomes effective and the stock price paid (or deemed to be paid) per share of the Company’s common stock in the corporate event, as described in the Indenture.

The Company may not redeem the 5.25% Notes prior to October 5, 2016. On or after October 5, 2016, the Company may, at its option, redeem for cash all or any portion of the 5.25% Notes if the closing sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which notice of redemption is provided, exceeds 160% of the conversion price on each applicable trading day. In the event of the Company’s redemption of the 5.25% Notes, the redemption price will equal 100% of the principal amount of the 5.25% Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. No sinking fund is provided for in the 5.25% Notes.

If the Company undergoes a fundamental change (as defined in the Indenture) prior to the maturity date of the 5.25% Notes, subject to certain conditions as described in the Indenture, holders may require the Company to purchase, for cash, all or any portion of their 5.25% Notes at a repurchase price equal to 100% of the principal amount of the 5.25% Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change purchase date.

The Indenture contains customary events of default with customary cure periods, including, without limitation, failure to make required payments or deliveries of shares of the Company’s common stock when due under the Indenture, failure to comply with certain covenants under the Indenture, failure to pay when due or acceleration of certain other indebtedness of the Company or certain of its subsidiaries, and certain events of bankruptcy and insolvency of the Company or certain of its subsidiaries. The occurrence of an event of default under the Indenture will allow either the trustee or the holders of at least 25% in principal amount of the then-outstanding 5.25% Notes to accelerate, or upon an event of default arising from certain events of bankruptcy or insolvency of the Company, will automatically cause the acceleration of, all amounts due under the 5.25% Notes. No events of default under the 5.25% Notes had occurred as of March 31, 2016.

The 5.25% Notes are senior unsecured obligations of the Company and rank senior in right of payment to the Company’s future indebtedness that is expressly subordinated in right of payment to the 5.25% Notes; equal in right of payment to the Company’s unsecured indebtedness that is not so subordinated; effectively junior to any of the Company’s secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness (including trade payables) of the Company’s subsidiaries.

On February 18, 2016, the Company paid $16,761 in cash to repurchase and retire $32,500 in principal amount of the 5.25% Notes, together with accrued and unpaid interest thereon, resulting in a $15,923 gain, net of related deferred financing costs.

Subsequent to March 31, 2016, on April 6, 2016, the Company repurchased and retired an additional $6,500 in principal amount of the 5.25% Notes, together with accrued and unpaid interest thereon, with $3,926 in cash, and on April 19, 2016, the Company entered into a privately negotiated exchange agreement with certain holders (the “Holders”) of the 5.25% Notes. Under the exchange agreement, the Holders agreed to exchange an aggregate principal amount of $25,000 of 5.25% Notes and accrued but unpaid interest in exchange for shares of the Company’s common stock (the “Shares”). Upon the consummation of all of the transactions contemplated by the exchange agreement, which occurred on May 4, 2016, the Company issued 6,265,829 shares to the Holders. Immediately following the exchange of the Notes contemplated by the exchange agreement, $186,000 in aggregate principal amount of the 5.25% Notes remained outstanding.

PlainsCapital Bank Credit Facility

On February 29, 2016, the Company entered into a Loan and Security Agreement (“LSA”) with PlainsCapital Bank (“Plains”), pursuant to which Plains agreed to lend the Company up to $50,000 on a revolving basis from time to time for a term of one year (the “Credit Facility”). All amounts advanced under the Credit Facility are due and payable on February 28, 2017. Simultaneously, the Company drew down $50,000 under this Credit Facility. The Credit Facility is evidenced by a promissory note the Company issued on February 29, 2016 in favor of Plains (the “Plains Note”). Interest on the Plains Note is payable monthly and accrues at a rate equal to the greater of (i) the then-current LIBOR rate plus 2.30% or (ii) 2.70%. As collateral security for the prompt payment in full when due of our obligations to Plains under the LSA and the Plains Note, the Company pledged to and granted Plains a security interest in all of its right, title and interest in the cash and corporate and municipal bonds rated AAA, AA or A by Standard & Poor’s Rating Services that the Company holds in an account at Plains. In connection with such pledge and security interest granted under the Credit Facility, on February 29, 2016, the Company entered into a Pledged Account Agreement with Plains and PlainsCapital Bank - Wealth Management and Trust (the “Pledge Agreement” and collectively with the LSA and the Plains Note, the “Plains Loan Documents”).The Plains Loan Documents include certain covenants and also provide 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 Credit Facility to become, or to be declared, due and payable. Events of default under the Plains Loan Documents include, among others, the occurrence of certain bankruptcy events, the failure to make payments when due under the Plains Note and the transfer or disposal of the collateral under the LSA. No events of default under the Plains Loan Documents had occurred as of March 31, 2016.

Canton Bonds

On March 19, 2014, Canton Renewables, LLC (“Canton”), a wholly owned subsidiary of the Company, completed the issuance of Solid Waste Facility Limited Obligation Revenue Bonds (Canton Renewables, LLC — Sauk Trail Hills Project) Series 2014 in the aggregate principal amount of $12,400 (the “Canton Bonds”).

The Canton Bonds were issued by the Michigan Strategic Fund (the “Issuer”) and the proceeds of such issuance were loaned by the Issuer to Canton pursuant to a loan agreement that became effective on March 19, 2014 (the “Loan Agreement”). The Canton Bonds are expected to be repaid from revenue generated by Canton from the sale of RNG and are secured by the revenue and assets of Canton. The Canton Bond repayments will be amortized through July 1, 2022, the average coupon interest rate on the Canton Bonds is 6.6%, and all but $1,000 of the principal amount of the Canton Bonds is non-recourse to Canton’s parent companies, including the Company.

Canton used the Canton Bond proceeds primarily to (i) refinance the cost of constructing and equipping its RNG extraction and production project in Canton, Michigan and (ii) pay a portion of the costs associated with the issuance of the Canton Bonds. The refinancing described in the prior sentence was accomplished through distributions to the Borrower’s direct and indirect parent companies who provided the financing for the RNG production facility, and such companies have used such distributions to finance construction of additional RNG extraction and processing projects and for working capital purposes.

The Loan Agreement contains customary events of default, with customary cure periods, including, without limitation, failure to make required payments when due under the Loan Agreement, failure to comply with certain covenants under the Loan Agreement, certain events of bankruptcy and insolvency of Canton, and the existence of an event of default under the indenture governing the Canton Bonds that was entered into between the Issuer and The Bank of New York Mellon Trust Company, N.A., as trustee. The occurrence of an event of default under the Loan Agreement will allow the Issuer or the trustee to accelerate all amounts due under the Loan Agreement. No events of default under the Loan Agreement had occurred as of March 31, 2016.

Other Debt

The Company has other debt due at various dates through 2020 bearing interest at rates up to 20.91% and with a weighted average interest rate of 6.35% and 6.65% as of December 31, 2015 and March 31, 2016, respectively.

December 2015 Termination of GE Credit Agreement

On November 7, 2012, the Company, through two wholly owned subsidiaries (the “Borrowers”), entered into a credit agreement (as amended, the “Credit Agreement”) with General Electric Capital Corporation (“GE”). Pursuant to the Credit Agreement, GE agreed to loan to the Borrowers up to an aggregate of $200,000 to finance the development, construction and operation of two LNG plants (individually a “Project” and together the “Projects”). Concurrently with the execution of the Credit Agreement, the Company issued to GE a warrant to purchase up to 5,000,000 shares of its common stock at a price of $0.01 per share (the "GE Warrant"). See Note 11 for further information.

On December 31, 2015, the Company terminated the Credit Agreement and related documents except for the GE Warrant, which remains outstanding, although 4,000,000 shares subject to the GE Warrant will not vest and will not become exercisable. No amounts had been borrowed by the Borrowers under the Credit Agreement as of its termination. As a result of the termination of the Credit Agreement, all related unamortized deferred financing costs that were to be amortized to interest expense in future periods have been eliminated from the balance sheet and a non-cash charge totaling $54.9 million was recorded in interest expense in the fourth quarter of 2015.

The Credit Agreement included a commitment fee on the unutilized loan amounts of 0.5% per annum, which was $250 for the three months ended March 31, 2015 and was charged to interest expense in the consolidated statement of operations.

Net Income (Loss) Per Share

3 Months Ended

Mar. 31, 2016

Earnings Per Share [Abstract]

Net Loss Per Share

et 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 each period. Diluted 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 and potentially dilutive securities outstanding during the period. Potentially dilutive securities include stock options, warrants, convertible notes and restricted stock units. The dilutive effect of stock options 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.

On December 31, 2015, the Company terminated the GE Credit Agreement and as a result, 4,000,000 shares of the 5,000,000 shares subject to the GE Warrant will not vest and will not become exercisable. The remaining 1,000,000 shares of common stock issuable upon exercise of the GE Warrant are included in the basic and diluted net income (loss) per share calculations, as 500,000 shares were exercisable as of the execution of the GE Credit Agreement and an additional 500,000 shares issuable upon exercise of the GE Warrant became exercisable on December 31, 2014. See Note 10 for further information. The information required to compute basic and diluted net income (loss) per share is as follows:



	Three Months Ended March 31,
	2015	2016
Basic weighted average number of common shares outstanding	91,317,053	97,178,768
Dilutive effect of potential common shares from restricted stock units (1)	—	2,643,076
Diluted weighted average number of common shares outstanding	91,317,053	99,821,844

(1) The Company recorded a net loss for the three months ended March 31, 2015 and therefore all potentially dilutive securities were excluded because their effect would have been antidilutive.

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



	Three Months Ended March 31,
	2015	2016
Options	11,172,586	11,740,308
Warrants	6,130,682	3,130,682
Convertible Notes	35,185,979	29,102,645
Restricted Stock Units	2,968,752	—

Stock-Based Compensation

3 Months Ended

Mar. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

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 condensed consolidated statements of operations during the periods:



	Three Months Ended March 31,
	2015		2016
Stock-based compensation expense	$	2,690	$	2,419
Stock-based compensation expense, net of $0 tax in 2015 and 2016	$	2,690	$	2,419

As of March 31, 2016, there was $14,005 of total unrecognized compensation cost related to non-vested shares underlying outstanding stock options and restricted stock units, which is expected to be expensed over a weighted-average period of approximately 2.1 years.

Environmental Matters, Litigation, Claims, Commitments and Contingencies	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Environmental Matters, Litigation, Claims, Commitments and Contingencies	Environmental Matters, Litigation, Claims, Commitments and Contingencies 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. The Company may become party to various legal actions that arise in the ordinary course of its business. During the course of its operations, the Company is also subject to audit by tax authorities for varying periods in various federal, state, local and foreign tax jurisdictions. Disputes may arise during the course of such audits as to facts and matters of law. It is impossible to determine the ultimate liabilities that the Company may incur resulting from any such lawsuits, claims and proceedings, audits, commitments, contingencies and related matters or the timing of these liabilities, if any. If these matters were to ultimately be resolved unfavorably, an outcome not currently anticipated, it is possible that such outcome could have a material adverse effect upon the Company’s consolidated financial position, results of operations, or liquidity. However, the Company believes that the ultimate resolution of such matters will not have a material adverse effect on the Company’s consolidated financial position, results of operations, or liquidity.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company’s income tax (expense) benefit for the three months ended March 31, 2015 and March 31, 2016 was $(854) and $(381), respectively. Tax expense for all periods was comprised of taxes due on the Company’s U.S. and foreign operations. The decrease in the Company’s income tax provision for the three months ended March 31, 2016 as compared to the tax provision for the three months ended March 31, 2015 was primarily attributed to a decrease in the earnings of foreign subsidiaries. The effective tax rate for the three months ended March 31, 2015 and 2016 are different from the federal statutory tax rate primarily as a result of losses for which no tax benefit has been recognized. The Company did not record a change in its liability for unrecognized tax benefits or penalties in the three months ended March 31, 2015 or March 31, 2016, and the net interest incurred was immaterial for such periods.

Fair Value Measurements

3 Months Ended

Mar. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements

air 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 nonrecurring 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.

As of March 31, 2016, the Company’s financial instruments consisted of available-for-sale securities, debt instruments, and liability-classified warrants (which include Series I Warrants). The Company’s available-for-sale securities 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 liability-classified warrants are classified within Level 3 because the Company uses the Black-Scholes model to estimate the fair value based on inputs that are not observable in any market. The fair value of the Company's debt instruments approximated their carrying values at December 31, 2015. As of March 31, 2016, the fair value of the Company's debt instruments approximated their carrying values, with the exception of the 5.25% Notes, for which the fair value was approximately $208,500 based on activity relating to such notes in April and May of 2016. See Note 10 for further information.

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, 2015 and March 31, 2016, respectively:



Description	Balance at December 31, 2015		Level 1		Level 2		Level 3
Assets:
Available-for-sale securities(1):
Certificate of deposits	$	48,551	$	—	$	48,551	$	—
Municipal bonds and notes	16,790		—		16,790		—
Zero coupon bonds	499		—		499		—
Corporate bonds	37,104		—		37,104		—
Liabilities:
Warrants(2)	632		—		—		632



Description	Balance at March 31, 2016	Level 1		Level 2	Level 3
Assets:
Available-for-sale securities(1):
Certificate of deposits	48,600	$	—	48,600	$	—
Municipal bonds and notes	11,549	—		11,549	—
Zero coupon bonds	1,000	—		1,000	—
U.S government agencies	5,002			5,002
Corporate bonds	9,545	—		9,545	—
Liabilities:
Warrants(2)	605	—		—	605

(1) Included in short-term investments in the condensed consolidated balance sheets. See Note 5 for further information.

(2) Included in accrued liabilities and other long-term liabilities in the condensed consolidated balance sheets.

Non-Financial Assets

No impairments of long-lived assets measured at fair value on a non-recurring basis have been incurred during the three months ended March 31, 2015 and 2016. The Company’s use of these non-financial assets does not differ from their highest and best use as determined from the perspective of a market participant.

- 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

Recently Adopted Accounting Changes and Recently Issued Accounting Standards	3 Months Ended
	Mar. 31, 2016
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Adopted Accounting Changes and Recently Issued Accounting Standards	Recently Adopted Accounting Changes and Recently Issued Accounting Standards In March 2016, the FASB issued Accounting Standards Update ("ASU") No. 2016-09, Compensation – Stock Compensation (Topic 718). The pronouncement was issued to simplify the accounting for share-based payment transactions, including income tax consequences, the classification of awards as either equity or liabilities, and the classification on the statement of cash flows. This pronouncement is effective for reporting periods beginning after December 15, 2016. Early adoption is allowed in an interim or annual accounting period. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases. The new standard will require most leases to be recognized on the balance sheet which will increase reported assets and liabilities. Lessor accounting remains substantially similar to current guidance. The new standard is effective for annual and interim periods in fiscal years beginning after December 15, 2018, which for the Company is the first quarter of fiscal 2019 and mandates a modified retrospective transition method. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures. In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. The new standard requires equity investments to be measured at fair value with changes in fair value recognized in net income, simplifies the impairment assessment of equity investments without readily determinable fair values, eliminates the requirement to disclose the methods and significant assumptions used to estimate fair value, requires use of the exit price notion when measuring fair value, requires separate presentation in certain financial statements, and requires an evaluation of the need for a valuation allowance on a deferred tax asset related to available-for-sale securities. The new standard is effective for fiscal years beginning after December 15, 2017, which for the Company is the first quarter of fiscal 2018. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers, Deferral of the Effective Date” which defers the new revenue guidance ASU 2014-09 to be effective for annual reporting periods beginning after 15 December 2017, including interim reporting periods within that reporting period, which for the Company is the first quarter of fiscal 2018, using one of two prescribed retrospective methods. In May 2014, the FASB issued ASU No. 2014-9, Revenue from Contracts with Customers, amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company is currently in the process of evaluating the impact of adoption on its consolidated financial statements and related disclosures. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures and has not yet selected a transition method. In August 2014, the FASB issued ASU No. 2014-15, to communicate amendments to FASB Accounting Standards Codification Subtopic 205-40, "Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern." The ASU requires management to evaluate relevant conditions, events and certain management plans that are known or reasonably knowable as of the evaluation date when determining whether substantial doubt about an entity's ability to continue as a going concern exists. Management will be required to make this evaluation for both annual and interim reporting periods. Management will need to make certain disclosures if it concludes that substantial doubt exists or when it plans to alleviate substantial doubt about the entity's ability to continue as a going concern. The standard is effective for annual periods ending after December 15, 2016 and for interim reporting periods starting in the first quarter of 2017. Early adoption is permitted. The Company does not expect the adoption of the guidance to have a material impact on its consolidated financial statements.

- Definition

The entire disclosure of changes in accounting principles, including adoption of new accounting pronouncements, that describes the new methods, amount and effects on financial statement line items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6507316

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Direct Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6510796

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=56949863&loc=d3e22583-107794

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Indirect Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6515603

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=56949863&loc=d3e22580-107794

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.10-01.(b)(6))
-URI http://asc.fasb.org/extlink&oid=27015980&loc=d3e46468-122699

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accounting Change
-URI http://asc.fasb.org/extlink&oid=6503790

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=56949863&loc=d3e22499-107794

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Retrospective Application
-URI http://asc.fasb.org/extlink&oid=6523989

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=51655806&loc=d3e765-108305

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=51655806&loc=d3e725-108305

+ Details

Alternative Fuels Excise Tax Credit	3 Months Ended
Alternative Fuels Excise Tax Credit	Mar. 31, 2016
Alternative Fuels Excise Tax Credit
Alternative Fuels Excise Tax Credit	Alternative Fuels Excise Tax Credit From October 1, 2006 through December 31, 2015, the Company was eligible to receive a federal alternative fuels tax credit (“VETC”) of $0.50 per gasoline gallon equivalent of CNG and $0.50 per liquid gallon of LNG that it sold as vehicle fuel. For 2016, the VETC credit is $0.50 per gasoline gallon equivalent of CNG and $0.50 per diesel gallon equivalent of LNG that is sold as a vehicle fuel. Based on the service relationship with its customers, either the Company or its customers claimed the credit. The Company records its VETC credits as revenue in its condensed consolidated statements of operations, as the credits are fully refundable and do not need to offset income tax liabilities to be received. In December 2015, the VETC was extended through December 31, 2016 and made retroactive to January 1, 2015. As a result, VETC revenues for the 2015 calendar year, totaling $30,986, were recognized in December 2015. The Company recognized $6,381 of VETC revenue during the three months ended March 31, 2016.

General (Policies)	3 Months Ended
General (Policies)	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation: The accompanying interim unaudited condensed 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 financial position, results of operations, comprehensive loss and cash flows as of and for the three months ended March 31, 2015 and 2016. All intercompany accounts and transactions have been eliminated in consolidation. The three month periods ended March 31, 2015 and 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any future year. Certain information and disclosures normally included in the notes to the financial statements have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”), but the resultant disclosures contained herein are in accordance with accounting principles generally accepted in the United States of America (“US GAAP”) as they apply to interim reporting. The condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the year ended December 31, 2015 that are included in the Company’s Annual Report on Form 10-K filed with the SEC on March 3, 2016.
Use of Estimates	Use of Estimates: The preparation of condensed consolidated financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and revenues and expenses recorded during the reporting period. Actual results could differ from those estimates. Significant estimates made in preparing the condensed consolidated financial statements include (but are not limited to) those related to revenue recognition, goodwill and long-lived intangible asset valuations and impairment assessments, income tax valuations, and stock-based compensation expense.
Revenue Recognition	Revenue Recognition: Effective January 1, 2016, the Company implemented a cost tracking system that provides for a detailed tracking of costs incurred on its station construction projects on a project by project basis. As a result of implementing this tracking system, the Company is able to make reliable estimates as to the percentage that a project is complete at the end of each reporting period. Beginning January 1, 2016, the Company began using the percentage of completion method to recognize revenue for station construction projects using the cost-to-cost method. Under this method, the Company estimates the percentage of completion based on the costs incurred to date for each contract in comparison to the estimated total costs for such contract at completion. The Company historically recognized revenue on station construction projects using the completed-contract method because it did not have a reliable means to make estimates of the percentage of the contract completed. Under the completed contract method, the construction projects were considered substantially complete at the earlier of customer acceptance of the fueling station or the time when the fuel dispensing activities began. The sale of compressors and related equipment continue to be recognized under the percentage of completion method as in previous periods. Station construction contracts are generally short-term with an exception for larger more complex stations, which can take up to 24 months to complete. Management evaluates the performance of contracts on an individual contract basis. Contract price and cost estimates are reviewed periodically as work progresses and adjustments proportionate to the percentage of completion are reflected in contract revenues in the reporting period when such estimates are revised. The nature of accounting for contracts is such that refinements of the estimating process for changing conditions and new developments are continuous and characteristic of the process. Many factors can and do change during a contract performance period which can result in a change to contract profitability including differing site conditions, the availability of skilled contract labor, the performance of major suppliers and subcontractors, and unexpected changes in material costs. These factors may result in revision to costs and income and are recognized in the period in which the revisions become known. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses become known. During the three months ended March 31, 2016, there were no losses on open contracts. The Company considers unapproved change orders to be contract variations for which the customer has approved the change of scope but the associated price change has not yet been agreed upon. Change orders that are unapproved as to both price and scope are evaluated as claims. Warranty claims have historically been insignificant. There were no significant unapproved change orders, claims, contract penalties, settlements or changes in contract estimates during the three months ended March 31, 2016. As a result of using the percentage of completion method to recognize revenues, station construction project sales during the three months ended March 31, 2016
Recently Adopted Accounting Changes and Recently Issued Accounting Standards	Recently Adopted Accounting Changes and Recently Issued Accounting Standards In March 2016, the FASB issued Accounting Standards Update ("ASU") No. 2016-09, Compensation – Stock Compensation (Topic 718). The pronouncement was issued to simplify the accounting for share-based payment transactions, including income tax consequences, the classification of awards as either equity or liabilities, and the classification on the statement of cash flows. This pronouncement is effective for reporting periods beginning after December 15, 2016. Early adoption is allowed in an interim or annual accounting period. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases. The new standard will require most leases to be recognized on the balance sheet which will increase reported assets and liabilities. Lessor accounting remains substantially similar to current guidance. The new standard is effective for annual and interim periods in fiscal years beginning after December 15, 2018, which for the Company is the first quarter of fiscal 2019 and mandates a modified retrospective transition method. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures. In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities. The new standard requires equity investments to be measured at fair value with changes in fair value recognized in net income, simplifies the impairment assessment of equity investments without readily determinable fair values, eliminates the requirement to disclose the methods and significant assumptions used to estimate fair value, requires use of the exit price notion when measuring fair value, requires separate presentation in certain financial statements, and requires an evaluation of the need for a valuation allowance on a deferred tax asset related to available-for-sale securities. The new standard is effective for fiscal years beginning after December 15, 2017, which for the Company is the first quarter of fiscal 2018. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers, Deferral of the Effective Date” which defers the new revenue guidance ASU 2014-09 to be effective for annual reporting periods beginning after 15 December 2017, including interim reporting periods within that reporting period, which for the Company is the first quarter of fiscal 2018, using one of two prescribed retrospective methods. In May 2014, the FASB issued ASU No. 2014-9, Revenue from Contracts with Customers, amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company is currently in the process of evaluating the impact of adoption on its consolidated financial statements and related disclosures. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures and has not yet selected a transition method. In August 2014, the FASB issued ASU No. 2014-15, to communicate amendments to FASB Accounting Standards Codification Subtopic 205-40, "Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern." The ASU requires management to evaluate relevant conditions, events and certain management plans that are known or reasonably knowable as of the evaluation date when determining whether substantial doubt about an entity's ability to continue as a going concern exists. Management will be required to make this evaluation for both annual and interim reporting periods. Management will need to make certain disclosures if it concludes that substantial doubt exists or when it plans to alleviate substantial doubt about the entity's ability to continue as a going concern. The standard is effective for annual periods ending after December 15, 2016 and for interim reporting periods starting in the first quarter of 2017. Early adoption is permitted. The Company does not expect the adoption of the guidance to have a material impact on its consolidated financial statements.

- Definition

Disclosure of accounting policy for revenue recognition for long-term construction-type contracts accounted for using the percentage-of-completion method. The disclosure would generally be expected to include the method or methods of measuring extent of progress toward completion. If the entity departs from using the percentage-of-completion method for a single contract or a group of contracts for which reasonably dependable estimates cannot be made, such a departure from the basic policy is disclosed. The disclosure may also describe the accounting for significant changes in estimate.

+ References + Details

Restricted Cash (Tables)

3 Months Ended

Mar. 31, 2016

Restricted Cash.

Schedule of components of restricted cash

Restricted cash consisted of the following as of December 31, 2015 and March 31, 2016:



	December 31, 2015		March 31, 2016
Short-term restricted cash:
Standby letters of credit	$	1,631	$	6,753
Canton Bonds (see Note 10)	2,609		2,022
Total short-term restricted cash	$	4,240	$	8,775

Investments (Tables)

3 Months Ended

Mar. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Summary of short-term investments

Short-term investments as of December 31, 2015 are summarized as follows:



	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value
Municipal bonds & notes	$	16,797	$	(7	)	$	16,790
Zero coupon bonds	500		(1		)	499
Corporate bonds	37,181		(77		)	37,104
Certificate of deposits	48,551		—			48,551
	$	103,029	$	(85	)	$	102,944

Short-term investments as of March 31, 2016 are summarized as follows:



	Amortized Cost		Gross Unrealized Losses			Estimated Fair Value
Municipal bonds & notes	$	11,558	$	(9	)	$	11,549
Zero coupon bonds	1,000		—			1,000
U.S. government agencies	5,000		2			$	5,002
Corporate bonds	9,548		(3		)	9,545
Certificate of deposits	48,600		—			48,600
	$	75,706	$	(10	)	$	75,696

Other Receivables (Tables)

3 Months Ended

Mar. 31, 2016

Receivables [Abstract]

Schedule of other receivables

Other receivables at December 31, 2015 and March 31, 2016 consisted of the following:



	December 31, 2015		March 31, 2016
Loans to customers to finance vehicle purchases	$	10,531	$	9,532
Accrued customer billings	7,106		7,610
Fuel tax and carbon credits	40,730		6,173
Other	2,300		2,730
	$	60,667	$	26,045

Inventory (Tables)

3 Months Ended

Mar. 31, 2016

Inventory Disclosure [Abstract]

Schedule of inventories

Inventories consisted of the following as of December 31, 2015 and March 31, 2016:



	December 31, 2015		March 31, 2016
Raw materials and spare parts	$	25,113	$	26,127
Work in process	973		2,742
Finished goods	3,203		1,168
	$	29,289	$	30,037

Land, Property and Equipment (Tables)

3 Months Ended

Mar. 31, 2016

Property, Plant and Equipment [Abstract]

Summary of land, property and equipment

Land, property and equipment at December 31, 2015 and March 31, 2016 are summarized as follows:



	December 31, 2015			March 31, 2016
Land	$	2,858		$	2,858
LNG liquefaction plants	94,634			94,634
RNG plants	46,397			46,397
Station equipment	316,258			317,387
Trailers	50,414			50,414
Other equipment	83,687			86,739
Construction in progress	139,586			139,099
	733,834			737,528
Less: accumulated depreciation	(217,510		)	(231,588		)
	$	516,324		$	505,940

Accrued Liabilities (Tables)

3 Months Ended

Mar. 31, 2016

Payables and Accruals [Abstract]

Schedule of accrued liabilities

Accrued liabilities at December 31, 2015 and March 31, 2016 consisted of the following:



	December 31, 2015		March 31, 2016
Salaries and wages	$	9,537	$	5,328
Accrued gas and equipment purchases	14,133		10,716
Accrued property and other taxes	5,344		4,038
Accrued professional fees	1,105		874
Accrued employee benefits	3,042		3,242
Accrued warranty liability	1,826		1,791
Accrued interest	3,718		5,995
Other	20,377		23,844
	$	59,082	$	55,828

Debt (Tables)

3 Months Ended

Mar. 31, 2016

Debt Disclosure [Abstract]

Schedule of debt and capital lease obligations

Debt and capital lease obligations at December 31, 2015 and March 31, 2016 consisted of the following and are further discussed below:



	December 31, 2015
	Principal Balances			Unamortized Debt Financing Costs			Balance, Net of Financing Costs
7.5% Notes(1)	$	150,000		399			149,601
SLG Notes	145,000			38			144,962
5.25% Notes	250,000			3,985			246,015
Canton Bonds	10,910			514			10,396
Capital lease obligations	6,448			—			6,448
Other debt	10,056			328			9,728
Total debt and capital lease obligations	572,414			5,264			567,150
Less amounts due within one year	(150,129		)	(273		)	(149,856		)
Total long-term debt and capital lease obligations	$	422,285		$	4,991		$	417,294



	March 31, 2016
	Principal Balances			Unamortized Debt Financing Costs			Balance Net of Financing Costs
7.5% Notes(1)	150,000			367			$	149,633
SLG Notes	85,000			14			84,986
5.25% Notes	217,500			3,129			214,371
PlainsCapital Bank Credit Facility	50,000			—			50,000
Canton Bonds	10,221			487			9,734
Capital lease obligations	6,437			—			6,437
Other debt	9,613			307			9,306
Total debt and capital lease obligations	528,771			4,304			524,467
Less amounts due within one year	(139,748		)	(243		)	(139,991		)
Total long-term debt and capital lease obligations	$	389,023		$	4,061		384,476

Net Income (Loss) Per Share (Tables)

3 Months Ended

Mar. 31, 2016

Earnings Per Share [Abstract]

Schedule of information required to compute basic and diluted earnings per share

The information required to compute basic and diluted net income (loss) per share is as follows:



	Three Months Ended March 31,
	2015	2016
Basic weighted average number of common shares outstanding	91,317,053	97,178,768
Dilutive effect of potential common shares from restricted stock units (1)	—	2,643,076
Diluted weighted average number of common shares outstanding	91,317,053	99,821,844

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



	Three Months Ended March 31,
	2015	2016
Options	11,172,586	11,740,308
Warrants	6,130,682	3,130,682
Convertible Notes	35,185,979	29,102,645
Restricted Stock Units	2,968,752	—

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

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



	Three Months Ended March 31,
	2015		2016
Stock-based compensation expense	$	2,690	$	2,419
Stock-based compensation expense, net of $0 tax in 2015 and 2016	$	2,690	$	2,419

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2016

Fair Value Disclosures [Abstract]

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, 2015 and March 31, 2016, respectively:



Description	Balance at December 31, 2015		Level 1		Level 2		Level 3
Assets:
Available-for-sale securities(1):
Certificate of deposits	$	48,551	$	—	$	48,551	$	—
Municipal bonds and notes	16,790		—		16,790		—
Zero coupon bonds	499		—		499		—
Corporate bonds	37,104		—		37,104		—
Liabilities:
Warrants(2)	632		—		—		632



Description	Balance at March 31, 2016	Level 1		Level 2	Level 3
Assets:
Available-for-sale securities(1):
Certificate of deposits	48,600	$	—	48,600	$	—
Municipal bonds and notes	11,549	—		11,549	—
Zero coupon bonds	1,000	—		1,000	—
U.S government agencies	5,002			5,002
Corporate bonds	9,545	—		9,545	—
Liabilities:
Warrants(2)	605	—		—	605

(1) Included in short-term investments in the condensed consolidated balance sheets. See Note 5 for further information.

(2) Included in accrued liabilities and other long-term liabilities in the condensed consolidated balance sheets.

General General (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Construction contracts, term	24 months
Debt issuance costs	$ 4,304	$ 5,264
New Accounting Pronouncement, Early Adoption, Effect \| Prepaid Expenses and Other Current Assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt issuance costs		(273)
New Accounting Pronouncement, Early Adoption, Effect \| Notes Receivable and Other Long-Term Assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt issuance costs		(4,991)
New Accounting Pronouncement, Early Adoption, Effect \| Current Portion of Long-Term Debt
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt issuance costs		273
New Accounting Pronouncement, Early Adoption, Effect \| Long Term Debt and Capital Lease Obligations Excluding Related Parties
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Debt issuance costs		$ 4,991
Percentage-of-Completion Method
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of change in method on revenues	9,393
Effect of change in method on operating income	$ 1,100
Effect of change in method on per diluted share amounts (in dollars per share)	$ 0.01

Investments in Other Entities and Noncontrolling Interest in a Subsidiary (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Oct. 14, 2014	Sep. 16, 2014
Acquisition and Divestitures
Income (loss) from equity method investment	$ (74,000)	$ (204,000)
Loss from noncontrolling interest	(299,000)	(380,000)
NG Advantage
Acquisition and Divestitures
Loss from noncontrolling interest	299,000	380,000
Noncontrolling interest, fair value	(26,094,000)		$ (26,393,000)
NG Advantage \| Common unit purchase agreement
Acquisition and Divestitures
Ownership interest acquired				53.30%
Mansfield
Acquisition and Divestitures
Ownership interest					50.00%
Income (loss) from equity method investment	(74,000)	$ (204,000)
Investment balance	$ 4,621,000		$ 4,695,000

Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash in excess of insurance limits	$ 84,841	$ 40,691

Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Restricted Cash
Short-term restricted cash	$ 8,775	$ 4,240
Canton Bonds
Restricted Cash
Short-term restricted cash	2,022	2,609
Standby letters of credit
Restricted Cash
Short-term restricted cash	$ 6,753	$ 1,631

Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Short-term investments
Amortized Cost	$ 75,706	$ 103,029
Gross Unrealized Losses	(10)	(85)
Estimated Fair Value	75,696	102,944
Municipal bonds & notes
Short-term investments
Amortized Cost	11,558	16,797
Gross Unrealized Losses	(9)	(7)
Estimated Fair Value	11,549	16,790
Zero coupon bonds
Short-term investments
Amortized Cost	1,000	500
Gross Unrealized Losses	0	(1)
Estimated Fair Value	1,000	499
U.S. government agencies
Short-term investments
Amortized Cost	5,000
Gross Unrealized Losses	2
Estimated Fair Value	5,002
Corporate bonds
Short-term investments
Amortized Cost	9,548	37,181
Gross Unrealized Losses	(3)	(77)
Estimated Fair Value	9,545	37,104
Certificate of deposits
Short-term investments
Amortized Cost	48,600	48,551
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 48,600	$ 48,551

Other Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Other Receivables
Other receivables	$ 26,045	$ 60,667
Loans to customers to finance vehicle purchases
Other Receivables
Other receivables	9,532	10,531
Accrued customer billings
Other Receivables
Other receivables	7,610	7,106
Fuel tax and carbon credits
Other Receivables
Other receivables	6,173	40,730
Other
Other Receivables
Other receivables	$ 2,730	$ 2,300

Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials and spare parts	$ 26,127	$ 25,113
Work in process	2,742	973
Finished goods	1,168	3,203
Total	$ 30,037	$ 29,289

Land, Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Land, Property and Equipment
Land, property and equipment, gross	$ 737,528		$ 733,834
Less: accumulated depreciation	(231,588)		(217,510)
Land, property and equipment, net	505,940		516,324
Capitalized software costs	23,384		22,886
Accumulated amortization on the capitalized software costs	14,731		13,793
Amortization expense related to the capitalized software costs	938	$ 716
Property and equipment purchases included in accounts payable and accrued liabilities	6,077	$ 13,771
Land
Land, Property and Equipment
Land, property and equipment, gross	2,858		2,858
LNG liquefaction plants
Land, Property and Equipment
Land, property and equipment, gross	94,634		94,634
RNG plants
Land, Property and Equipment
Land, property and equipment, gross	46,397		46,397
Station equipment
Land, Property and Equipment
Land, property and equipment, gross	317,387		316,258
Trailers
Land, Property and Equipment
Land, property and equipment, gross	50,414		50,414
Other equipment
Land, Property and Equipment
Land, property and equipment, gross	86,739		83,687
Construction in progress
Land, Property and Equipment
Land, property and equipment, gross	$ 139,099		$ 139,586

Investments in Other Entities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Equity method investments
Income (loss) from equity method investment	$ (74)	$ (204)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Salaries and wages	$ 5,328	$ 9,537
Accrued gas and equipment purchases	10,716	14,133
Accrued property and other taxes	4,038	5,344
Accrued professional fees	874	1,105
Accrued employee benefits	3,242	3,042
Accrued warranty liability	1,791	1,826
Accrued interest	5,995	3,718
Other	23,844	20,377
Total	$ 55,828	$ 59,082

Debt - Other Debt (Details) - USD ($) $ in Thousands	Apr. 20, 2016	Apr. 19, 2016	Mar. 31, 2016	Feb. 29, 2016	Dec. 31, 2015
Long-term debt
Principal Balances			$ 528,771		$ 572,414
Unamortized Debt Financing Costs			4,304		5,264
Balance, Net of Financing Costs			524,467		567,150
Principal Balances, amounts due within one year			(139,748)		(150,129)
Unamortized Debt Financing Costs, amounts due within one year			(243)		(273)
Balance, Net of Financing Costs, amounts due within one year			(139,991)		(149,856)
Principal Balances, long-term			389,023		422,285
Unamortized Debt Financing Costs, long-term			4,061		4,991
Balance, Net of Financing Costs, long-term			384,476		417,294
Related party notes			65,000		65,000
7.5% Notes
Long-term debt
Principal Balances			150,000		150,000
Unamortized Debt Financing Costs			367		399
Balance, Net of Financing Costs			149,633		149,601
SLG Notes
Long-term debt
Principal Balances			85,000		145,000
Unamortized Debt Financing Costs			14		38
Balance, Net of Financing Costs			84,986		144,962
Aggregate principal amount				$ 145,000
5.25% Notes
Long-term debt
Principal Balances			217,500		250,000
Unamortized Debt Financing Costs			3,129		3,985
Balance, Net of Financing Costs			214,371		246,015
5.25% Notes \| Subsequent Event
Long-term debt
Aggregate principal amount	$ 186,000	$ 25,000
Canton Bonds
Long-term debt
Principal Balances			10,221		10,910
Unamortized Debt Financing Costs			487		514
Balance, Net of Financing Costs			9,734		10,396
Capital lease obligations
Long-term debt
Principal Balances			6,437		6,448
Unamortized Debt Financing Costs			0		0
Balance, Net of Financing Costs			6,437		6,448
Other debt
Long-term debt
Principal Balances			9,613		10,056
Unamortized Debt Financing Costs			307		328
Balance, Net of Financing Costs			9,306		$ 9,728
PlainsCapital Bank Credit Facility
Long-term debt
Principal Balances			50,000
Unamortized Debt Financing Costs			0
Balance, Net of Financing Costs			$ 50,000

Debt - 7.5% Notes (Details) - 7.5% Notes	Aug. 27, 2013 USD ($) shares	Jun. 14, 2013 USD ($) day $ / shares	Jul. 11, 2011 USD ($) note
Long-term debt
Financing commitment received			$ 150,000,000
Number of debt instruments \| note			3
Financing commitment, issuance period			3 years
Principal amount of each debt instrument to be issued			$ 50,000,000
Interest rate			7.50%
Boone Pickens
Long-term debt
Aggregate principal amount	$ 65,000,000
Boone Pickens \| Common stock
Long-term debt
Number of shares of common stock into which Notes are convertible \| shares	4,113,924
Buyers
Long-term debt
Additional amount of advances under the obligation assumed		$ 50,000,000
Amount of advance funded		$ 50,000,000
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 \| day		20
Number of consecutive trading days used to determine the conversion obligation on the notes for the Company to force conversion		30 days
Period during which the debt instrument principal balance is required to be paid following its issuance		7 years
Green Energy Investment Holdings, LLC
Long-term debt
Principal amount transferred	$ 5,000,000
Aggregate principal amount	$ 80,000,000
Green Energy Investment Holdings, LLC \| Common stock
Long-term debt
Number of shares of common stock into which Notes are convertible \| shares	5,063,291
Other Third Parties
Long-term debt
Aggregate principal amount	$ 5,000,000
Other Third Parties \| Common stock
Long-term debt
Number of shares of common stock into which Notes are convertible \| shares	316,456

Debt - SLG Notes (Details) - SLG Notes			1 Months Ended	2 Months Ended
Debt - SLG Notes (Details) - SLG Notes	Feb. 29, 2016 USD ($)	Aug. 24, 2011 USD ($) day $ / shares	Apr. 30, 2012 USD ($) shares	Feb. 28, 2013 USD ($) shares	Mar. 01, 2012 USD ($)
Long-term debt
Financing commitment received		$ 150,000,000
Interest rate		7.50%
Conversion price of shares (in dollars per share) \| $ / shares		$ 15.00
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 \| day		20
Number of consecutive trading days used to determine the conversion obligation on the notes for the Company to force conversion		30 days
Period during which the debt instrument principal balance is required to be paid following its issuance		5 years
Repayments of debt	$ 60,000,000
Aggregate principal amount	145,000,000
Repayment of accrued interest	$ 1,812,000
Common stock
Long-term debt
Amount of principal and accrued interest under debt conversion			$ 1,003,000	$ 4,030,000
Common stock issued upon conversion of debt (in shares) \| shares			66,888	268,664
Baytree Investments (Mauritius) Pte Ltd
Long-term debt
Principal amount transferred					$ 24,000,000

Debt - 5.25% Notes (Details)				1 Months Ended	3 Months Ended
Debt - 5.25% Notes (Details)	May 04, 2016 shares	Apr. 06, 2016 USD ($)	Feb. 18, 2016 USD ($)	Sep. 30, 2013 USD ($) day $ / shares	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Apr. 20, 2016 USD ($)	Apr. 19, 2016 USD ($)
Long-term debt
Gain from extinguishment of debt					$ 15,923,000	$ 0
Subsequent Event
Long-term debt
Shares issued upon conversion of debt \| shares	6,265,829
5.25% Notes
Long-term debt
Debt issuance amount				$ 250,000
Interest rate				5.25%
Payment of certain debt issuance costs				$ 7,805,000
Amount of advance funded				$ 242,195,000
Conversion rate of debt instrument (shares per USD)				0.0641026
Conversion price of shares (in dollars per share) \| $ / shares				$ 15.60
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 \| day				20
Number of consecutive trading days used to determine the conversion obligation on the notes for the Company to force conversion				30 days
Percentage of the trade price of common stock that the conversion price must be at premium for the Company to force conversion				160.00%
Redemption price as percentage of principal amount of notes to be redeemed				100.00%
Amount of sinking fund					$ 0
Percentage of principal amount at which notes may be required to be repurchased in event of fundamental change by the entity				100.00%
Repayments of debt			$ 16,761,000
Amount of par value debt retired			32,500,000
Gain from extinguishment of debt			$ 15,923,000
5.25% Notes \| Subsequent Event
Long-term debt
Repayments of debt		$ 3,926,000
Amount of par value debt retired		$ 6,500,000
Aggregate principal amount							$ 186,000,000	$ 25,000,000
5.25% Notes \| Minimum
Long-term debt
Percentage of principal amount of notes outstanding allowing holders to accelerate all amounts due under notes in event of default under the Indenture				25.00%

Debt - PlainsCapital Bank Credit Facility (Details) - Plains Capital Bank Credit Agreement	Feb. 29, 2016 USD ($)
Long-term debt
Line of credit limit	$ 50,000,000
Interest rate	2.70%
LIBOR
Long-term debt
Percentage of margin added to reference rate to determine interest rate on debt	2.30%

Debt - Canton Bonds (Details) - USD ($)	3 Months Ended
Debt - Canton Bonds (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015	Mar. 19, 2014
Canton Bonds
Long-term debt
Principal amount with recourse to the Company			$ 1,000,000
Canton Bonds \| Canton Renewables
Long-term debt
Debt issuance amount			$ 12,400,000
Coupon interest rate			6.60%
Other debt
Long-term debt
Maximum effective percentage rate	20.91%
Weighted average interest rate	6.65%	6.35%

Debt - GE Credit Agreement (Details) - GE Credit Agreement $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
	Nov. 07, 2012 USD ($) subsidiary project $ / shares shares	Dec. 31, 2015 USD ($) shares	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)
Long-term debt
Number of wholly owned subsidiaries through which the entity entered into a financing arrangement \| subsidiary	2
Line of credit limit	$ 200,000
Number of LNG production facilities being financed \| project	2
Write off of deferred debt issuance cost		$ 54,900
Commitment fee on the unutilized loan amounts	0.50%
Commitment fee			$ 0	$ 1,014	$ 1,014
Common stock \| GE Warrant
Long-term debt
Number of shares issuable upon exercise of warrants (up to) \| shares	5,000,000	5,000,000		5,000,000
Exercise price of warrants (in dollars per share) \| $ / shares	$ 0.01
Number of warrants which will not vest and will not become exercisable \| shares		4,000,000		4,000,000

Net Income (Loss) Per Share (Details) - shares			3 Months Ended
Net Income (Loss) Per Share (Details) - shares	Dec. 31, 2014	Sep. 11, 2014	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Nov. 07, 2012
Basic and diluted:
Basic weighted average number of common shares outstanding			97,178,768	91,317,053
Dilutive effect of potential common shares from restricted stock units			2,643,076	0
Diluted weighted average number of common shares outstanding			99,821,844	91,317,053
Common stock \| GE Credit Agreement \| GE Warrant
Number of shares issuable upon exercise of warrants (up to)					5,000,000	5,000,000
Number of shares included in weighted average share calculation		1,000,000
Number of shares that became exercisable in the period		500,000
Number of additional shares that became exercisable in the period	500,000
Number of warrants which will not vest and will not become exercisable					4,000,000

Net Loss Per Share - Anti-dilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Options
Net Loss Per Share
Anti-dilutive securities (in shares)	11,740,308	11,172,586
Warrants
Net Loss Per Share
Anti-dilutive securities (in shares)	3,130,682	6,130,682
Convertible Notes
Net Loss Per Share
Anti-dilutive securities (in shares)	29,102,645	35,185,979
Restricted Stock Units
Net Loss Per Share
Anti-dilutive securities (in shares)	0	2,968,752

Stock-Based Compensation (Details) - USD ($)	3 Months Ended
Stock-Based Compensation (Details) - USD ($)	Mar. 31, 2016	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense	$ 2,419,000	$ 2,690,000
Stock-based compensation expense, net of $0 tax in 2015 and 2016	2,419,000	2,690,000
Tax benefit from compensation expense	0	$ 0
Unrecognized compensation cost	$ 14,005,000
Unrecognized compensation cost, weighted-average period	2 years 1 month 17 days

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income tax (expense) benefit	$ (381)	$ (854)

Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value Measurements
Debt and Capital Lease Obligations	$ 524,467	$ 567,150
Fair value measured on recurring basis \| Certificate of deposits
Assets:
Available-for-sale securities	48,600	48,551
Fair value measured on recurring basis \| Municipal bonds & notes
Assets:
Available-for-sale securities	11,549	16,790
Fair value measured on recurring basis \| Zero coupon bonds
Assets:
Available-for-sale securities	1,000	499
Fair value measured on recurring basis \| Corporate bonds
Assets:
Available-for-sale securities	9,545	37,104
Fair value measured on recurring basis \| U.S. government agencies
Assets:
Available-for-sale securities	5,002
Fair value measured on recurring basis \| Warrants
Liabilities:
Warrants	605	632
Fair value measured on recurring basis \| Level 2 \| Certificate of deposits
Assets:
Available-for-sale securities	48,600	48,551
Fair value measured on recurring basis \| Level 2 \| Municipal bonds & notes
Assets:
Available-for-sale securities	11,549	16,790
Fair value measured on recurring basis \| Level 2 \| Zero coupon bonds
Assets:
Available-for-sale securities	1,000	499
Fair value measured on recurring basis \| Level 2 \| Corporate bonds
Assets:
Available-for-sale securities	9,545	37,104
Fair value measured on recurring basis \| Level 2 \| U.S. government agencies
Assets:
Available-for-sale securities	5,002
Fair value measured on recurring basis \| Level 3 \| Warrants
Liabilities:
Warrants	605	632
5.25% Notes
Fair Value Measurements
Debt and Capital Lease Obligations	214,371	$ 246,015
5.25% Notes \| Fair value measured on recurring basis
Fair Value Measurements
Debt and Capital Lease Obligations	$ 208,500

Alternative Fuels Excise Tax Credit (Details) $ in Thousands	3 Months Ended	12 Months Ended	111 Months Ended
	Mar. 31, 2016 USD ($) $ / gallon	Dec. 31, 2015 USD ($)	Dec. 31, 2015 $ / gallon
Alternative Fuels Excise Tax Credit
Federal fuel tax credit - CNG (in dollars per gasoline gallon equivalent)	0.50		0.50
Federal fuel tax credit - LNG (in dollars per liquid gallon)	0.50		0.50
VETC credits recognized as revenue \| $	$ 6,381	$ 30,986