Via Renewables (VIASP) 10-K 9 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Mar. 07, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	SPKE
Entity Registrant Name	Spark Energy, Inc.
Entity Central Index Key	1,606,268
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Class of Stock [Line Items]
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 215
Common Class A
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		13,135,636
Common Class B
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		21,485,126

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS		Dec. 31, 2017USD ($)		Dec. 31, 2016USD ($)
Current assets:
Cash and cash equivalents	[1]	$ 29,419,000		$ 18,960,000	[2]
Accounts receivable, net of allowance for doubtful accounts of $4.0 million and $2.3 million as of December 31, 2017 and 2016, respectively		158,814,000		112,491,000
Accounts receivable—affiliates		3,661,000		2,624,000
Inventory		4,470,000		3,752,000
Fair value of derivative assets		31,191,000		8,344,000
Customer acquisition costs, net		22,123,000		18,834,000
Customer relationships, net		18,653,000		12,113,000
Prepaid assets		1,028,000		1,361,000
Deposits		7,701,000		7,329,000
Other current assets		19,678,000		12,175,000
Total current assets		296,738,000		197,983,000
Property and equipment, net		8,275,000		4,706,000
Fair value of derivative assets		3,309,000		3,083,000
Customer acquisition costs, net		6,949,000	[3]	6,134,000
Deferred tax assets		34,839,000		21,410,000
Deferred tax assets		24,185,000		54,109,000
Goodwill		120,154,000		79,147,000
Other assets		11,500,000		8,658,000
Total Assets		505,949,000		375,230,000
Current liabilities:
Accounts payable		77,510,000		52,309,000
Accounts payable—affiliates		4,622,000		3,775,000
Accrued liabilities		33,679,000		36,619,000
Fair value of derivative liabilities		1,637,000		680,000
Current payable pursuant to tax receivable agreement—affiliates		7,500,000		51,287,000
Current payable pursuant to tax receivable agreement—affiliates		5,937,000		0
Current contingent consideration for acquisitions		4,024,000		11,827,000
Current portion of note payable		13,443,000		15,501,000
Convertible subordinated notes to affiliates		0		6,582,000
Other current liabilities		2,675,000		5,476,000
Total current liabilities		151,027,000		184,056,000
Long-term liabilities:
Fair value of derivative liabilities		492,000		68,000
Payable pursuant to tax receivable agreement—affiliates		26,355,000		49,886,000
Long-term portion of Senior Credit Facility		117,750,000		0
Subordinated debt—affiliate		0		5,000,000
Contingent consideration for acquisitions		626,000		10,826,000
Other long-term liabilities		172,000		1,658,000
Long-term portion of note payable		7,051,000		0
Total liabilities		303,473,000		251,494,000
Commitments and contingencies
Series A Preferred Stock, par value $0.01 per share, 20,000,000 shares authorized, 1,704,339 shares issued and outstanding at December 31, 2017 and zero shares issued and outstanding at December 31, 2016		41,173,000		0
Additional paid-in capital (1)	[4]	26,914,000		25,272,000
Accumulated other comprehensive (loss)/income		(11,000)		11,000
Retained earnings		11,008,000		4,711,000
Treasury stock, at cost, 99,446 shares at December 31, 2017 and zero shares at December 31, 2016		(2,011,000)		0
Total stockholders' equity		36,248,000		30,330,000
Non-controlling interest in Spark HoldCo, LLC (1)	[4]	125,055,000		93,406,000
Total equity		161,303,000		123,736,000
Total Liabilities, Series A Preferred Stock and stockholders' equity		505,949,000		375,230,000
Common Class A
Common stock	[4]	132,000		130,000
Common Class B
Common stock	[4]	$ 216,000		$ 206,000
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	See Note 4 "Equity" for disclosure of our variable interest entity in Spark HoldCo, LLC.
[4]	Outstanding shares of common stock, additional paid-in capital and non-controlling interest reflect the two-for-one stock split, which took effect on June 16, 2017. See Note 4 "Equity" for further discussion

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts	$ 4	$ 2.3
Preferred stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	1,704,339	0
Preferred stock, shares outstanding (in shares)	1,704,339	0
Treasury stock, shares (in shares)	99,446	0
Common Class A
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	120,000,000	120,000,000
Common stock, shares issued (in shares)	13,235,082	12,993,118
Common stock, shares outstanding (in shares)	13,135,636	12,993,118
Common Class B
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	21,485,126	20,449,484
Common stock, shares outstanding (in shares)	21,485,126	20,449,484

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	[2]	Dec. 31, 2015	[3]
Revenues:
Retail revenues		$ 798,772	[1]	$ 547,283		$ 356,659
Net asset optimization (expense)/revenues	[4]	(717)	[1]	(586)		1,494
Total Revenues		798,055	[1]	546,697		358,153
Operating Expenses:
Retail cost of revenues	[5]	552,167	[1]	344,944		241,188
General and administrative	[6]	101,127	[1]	84,964		61,682
Depreciation and amortization		42,341	[1]	32,788		25,378
Total Operating Expenses		695,635	[1]	462,696		328,248
Operating income		102,420	[1]	84,001		29,905
Other (expense)/income:
Interest expense		(11,134)	[1]	(8,859)		(2,280)
Change in tax receivable agreement liability		22,267	[1],[7]	0	[8]	0	[9]
Interest and other income		256	[1]	957		324
Total other expenses		11,389	[1]	(7,902)		(1,956)
Income before income tax expense		113,809	[1]	76,099		27,949
Income tax expense		37,528	[1]	10,426		1,974
Net income		76,281	[1],[7],[10]	65,673	[8],[11]	25,975	[9],[12]
Less: Net income attributable to non-controlling interests		57,427	[1]	51,229		22,110
Net income attributable to Spark Energy, Inc. stockholders		18,854	[1]	14,444		3,865
Less: Dividend on Series A preferred stock	[1]	3,038		0		0
Net income attributable to stockholders of Class A common stock		15,816	[1]	14,444		3,865
Other comprehensive (loss) income, net of tax:
Currency translation (loss) gain		(59)	[1]	41		0
Other comprehensive (loss) income		(59)	[1]	41		0
Comprehensive income		76,222	[1]	65,714		25,975
Less: Comprehensive income attributable to non-controlling interests		57,390	[1]	51,259		22,110
Comprehensive income attributable to Spark Energy, Inc. stockholders		$ 18,832	[1]	$ 14,455		$ 3,865
Net income attributable to Spark Energy, Inc. per share of Class A common stock
Basic (in dollars per share)		$ 1.20	[1]	$ 1.27		$ 0.63
Diluted (in dollars per share)		$ 1.19	[1]	$ 1.11		$ 0.53
Weighted average shares of Class A common stock outstanding
Basic (in shares)		13,143	[1]	11,402		6,129
Diluted (in shares)		13,346	[1]	12,690		6,655
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[4]	Net asset optimization revenues includes asset optimization (expense)/revenues—affiliates of $1,334, $154 and $1,101 for the years ended December 31, 2017, 2016 and 2015, respectively, and asset optimization revenues—affiliates cost of revenues of $53, $1,633 and $11,285 for the years ended December 31, 2017, 2016 and 2015, respectively.
[5]	Retail cost of revenues includes retail cost of revenues—affiliates of $0, $9 and $17 for the years December 31, 2017, 2016 and 2015, respectively.
[6]	General and administrative includes general and administrative expense—affiliates of $24,700, $15,700 and $0 for the years ended December 31, 2017, 2016 and 2015, respectively.
[7]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[8]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[9]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.
[10]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[11]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[12]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

CONSOLIDATED STATEMENTS OF OPE5

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - Footnotes - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Asset optimization revenues - affiliates	[2]	$ (717)	[1]	$ (586)	[3]	$ 1,494	[4]
Retail cost of revenues - affiliates	[5]	552,167	[1]	344,944	[3]	241,188	[4]
General and administrative expense - affiliates	[6]	101,127	[1]	84,964	[3]	61,682	[4]
Affiliated Entity
Asset optimization revenues - affiliates		1,334		154		1,101
Cost of revenue - affiliates		53		1,633		11,285
Retail cost of revenues - affiliates		0		9		17
General and administrative expense - affiliates		$ 24,700		$ 15,700		$ 0
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Net asset optimization revenues includes asset optimization (expense)/revenues—affiliates of $1,334, $154 and $1,101 for the years ended December 31, 2017, 2016 and 2015, respectively, and asset optimization revenues—affiliates cost of revenues of $53, $1,633 and $11,285 for the years ended December 31, 2017, 2016 and 2015, respectively.
[3]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[4]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[5]	Retail cost of revenues includes retail cost of revenues—affiliates of $0, $9 and $17 for the years December 31, 2017, 2016 and 2015, respectively.
[6]	General and administrative includes general and administrative expense—affiliates of $24,700, $15,700 and $0 for the years ended December 31, 2017, 2016 and 2015, respectively.

CONSOLIDATED STATEMENT OF CHANG

CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) shares in Thousands, $ in Thousands		Total		Common StockCommon Class A		Common StockCommon Class B		Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Additional Paid-In Capital	[1]	Retained Earnings (Deficit)	Total Stockholders' Equity	Non-controlling Interest	[1]
Balance at beginning of period at Dec. 31, 2014		$ 24,117		$ 60	[1]	$ 216	[1]	$ 0	$ 0	$ 9,158		$ (775)	$ 8,659	$ 15,458
Balance at beginning of period (in shares) at Dec. 31, 2014				6,000	[1]	21,500	[1]	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation		2,165								2,165			2,165
Restricted stock unit vesting		187		$ 2	[1]					185			187
Restricted stock unit vesting (in shares)	[1]			238
Contribution from NuDevco		129								129			129
Consolidated net income (loss)	[4]	25,975	[2],[3]									3,865	3,865	22,110
Beneficial conversion feature		789								789			789
Distributions paid to Class B non-controlling unit holders		(15,587)												(15,587)
Net contribution by NG&E	[2]	0
Net contribution of the Major Energy Companies	[2]	0
Dividends paid to Class A common shareholders		(4,456)										(4,456)	(4,456)
Balance at end of period at Dec. 31, 2015		33,319		$ 62	[1]	$ 216	[1]	$ 0	0	12,426		(1,366)	11,338	21,981
Balance at end of period (in shares) at Dec. 31, 2015				6,238	[1]	21,500	[1]	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation		2,270								2,270			2,270
Restricted stock unit vesting		1,062		$ 4	[1]					1,058			1,062
Restricted stock unit vesting (in shares)	[1]			305
Excess tax benefit related to restricted stock vesting		186								186			186
Consolidated net income (loss)	[7]	65,673	[5],[6]									14,444	14,444	51,229
Foreign currency translation adjustment for equity method investee		41							11				11	30
Beneficial conversion feature		243								243			243
Distributions paid to Class B non-controlling unit holders		(34,931)												(34,931)
Net contribution by NG&E	[5]	0
Net contribution of the Major Energy Companies		3,873	[5]											3,873
Dividends paid to Class A common shareholders		(8,367)										(8,367)	(8,367)
Tax impact from tax receivable agreement upon exchange of units of Spark HoldCo, LLC to shares of Class A Common Stock		4,768								4,768			4,768
Exchange of shares of Class B common stock to shares of Class A common stock		0		$ 64	[1]	$ (64)	[1]			2,716			2,716	(2,716)
Exchange of shares of Class B common stock to shares of Class A common stock (in shares)	[1]			6,450		(6,450)
Proceeds from disgorgement of stockholder short-swing profits		1,605								1,605			1,605
Issuance of Class B Common Stock		53,994				$ 54	[1]						54	53,940
Issuance of Class B Common Stock (in shares)	[1]					5,400
Balance at end of period at Dec. 31, 2016		123,736		$ 130	[1]	$ 206	[1]	$ 0	11	25,272		4,711	30,330	93,406
Balance at end of period (in shares) at Dec. 31, 2016				12,993	[1]	20,450	[1]	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation		2,754								2,754			2,754
Restricted stock unit vesting		1,054		$ 2	[1]					1,052			1,054
Restricted stock unit vesting (in shares)	[1]			242
Consolidated net income (loss)	[8]	76,281	[9],[10]									18,854	18,854	57,427
Foreign currency translation adjustment for equity method investee		(59)							(22)				(22)	(37)
Distributions paid to Class B non-controlling unit holders		(33,800)												(33,800)
Net contribution by NG&E		274	[9]											274
Net contribution of the Major Energy Companies	[9]	0
Dividends paid to Class A common shareholders		(9,519)										(9,519)	(9,519)
Dividends to Preferred Stock		(3,038)										(3,038)	(3,038)
Proceeds from disgorgement of stockholder short-swing profits		708								708			708
Tax receivable agreement liability true-up		(2,872)	[1]							(2,872)			(2,872)
Issuance of Class B Common Stock		7,795				$ 10	[1]						10	7,785
Issuance of Class B Common Stock (in shares)	[1]					1,035
Treasury Stock		(2,011)						$ (2,011)					(2,011)
Treasury Stock (in shares)								(99)
Balance at end of period at Dec. 31, 2017		$ 161,303		$ 132	[1]	$ 216	[1]	$ (2,011)	$ (11)	$ 26,914		$ 11,008	$ 36,248	$ 125,055
Balance at end of period (in shares) at Dec. 31, 2017				13,235	[1]	21,485	[1]	99
[1]	Outstanding shares of common stock, additional paid-in capital and non-controlling interest have been retrospectively adjusted to reflect the two-for-one stock split, which took effect on June 16, 2017. See Note 4 "Equity" for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[4]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[5]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[6]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[7]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[8]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[9]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[10]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	[2]	Dec. 31, 2016USD ($)	[4]	Dec. 31, 2015USD ($)	[7]
Cash flows from operating activities:
Net income	$ 76,281	[1],[3]	$ 65,673	[5],[6]	$ 25,975	[8],[9]
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization expense	42,666		48,526		25,378
Deferred income taxes	28,584		3,382		1,340
Change in Tax Receivable Agreement liability	(22,267)	[3]	0	[5]	0	[8]
Stock based compensation	5,058		5,242		3,181
Amortization of deferred financing costs	1,035		668		412
Change in fair value of Earnout liabilities	(7,898)		(297)		0
Accretion on fair value of Earnout liabilities	4,108		5,060		0
Excess tax benefit related to restricted stock vesting	179		0		0
Bad debt expense	6,550		1,261		7,908
(Gain) loss on derivatives, net	(5,008)		(22,407)		18,497
Current period cash settlements on derivatives, net	(19,598)		(24,427)		(23,948)
Accretion of discount to convertible subordinated notes to affiliate	1,004		0		0
Other	(5)		(407)		(1,320)
Changes in assets and liabilities:
Decrease in restricted cash	0		0		707
(Increase) decrease in accounts receivable	(32,361)		(12,088)		7,876
Increase in accounts receivable—affiliates	(1,459)		(118)		(608)
(Increase) decrease in inventory	(718)		542		4,544
Increase in customer acquisition costs	(25,874)		(21,907)		(19,869)
Decrease in prepaid and other current assets	1,915		71		10,845
(Increase) decrease in other assets	(465)		1,321		(1,101)
Increase in customer relationships and trademarks	0		0		(2,776)
Increase (decrease) in accounts payable and accrued liabilities	14,831		14,831		(13,307)
Increase in accounts payable—affiliates	51		458		944
(Decrease) increase in other current liabilities	(1,210)		2,364		(645)
(Decrease) increase in other non-current liabilities	(1,487)		45		1,898
Net cash provided by operating activities	63,912		67,793		45,931
Cash flows from investing activities:
Purchases of property and equipment	(1,704)		(2,258)		(1,766)
Acquisitions of Perigee and other customers	(11,759)		0		0
Acquisition of the Verde Companies	(69,538)		0		0
Contribution to equity method investment	0		(1,102)		(330)
Net cash used in investing activities	(97,757)		(36,344)		(41,943)
Cash flows from financing activities:
Proceeds from issuance of Series A Preferred Stock, net of issuance costs paid	40,241		0		0
Borrowings on notes payable	206,400		79,048		59,224
Payments on notes payable	(152,939)		(66,652)		(49,826)
Issuance of convertible subordinated notes to affiliate	0		0		7,075
Restricted stock vesting	(3,091)		(1,183)		(432)
Contributions from NuDevco	0		0		129
Proceeds from disgorgement of stockholders short-swing profits	1,129		941		0
Excess tax benefit related to restricted stock vesting	0		185		0
Payment of dividends to Class A common shareholders	(9,519)		(8,367)		(4,456)
Payment of distributions to non-controlling unitholders	(33,800)		(34,930)		(15,587)
Payment of dividends to Preferred Stock	(2,106)		0		0
Purchase of Treasury Stock	(2,011)		0		0
Net cash provided by (used in) financing activities	44,304		(16,963)		(3,873)
Increase in Cash and cash equivalents and Restricted Cash	10,459		14,486		115
Cash and cash equivalents and Restricted cash—beginning of period	18,960	[4]	4,474	[7]	4,359
Cash and cash equivalents and Restricted cash—end of period	29,419		18,960	[2]	4,474	[4]
Non-cash items:
Assumption of legal liability in connection with the Major Energy Companies acquisition	0		5,000		0
Net contribution of the Major Energy Companies	0		3,873		0
Net contribution by NG&E in excess of cash	274		0		0
Tax benefit from tax receivable agreement	(1,802)		31,490		(64)
Liability due to tax receivable agreement	4,674		(26,722)		(55)
Property and equipment purchase accrual	91		(32)		45
CenStar Earnout accrual	0		0		500
Cash paid during the period for:
Interest	5,715		2,280		1,661
Taxes	11,205		7,326		216
Common Class B
Cash flows from financing activities:
Proceeds from issuance of Class B common stock	0		13,995		0
Non-cash items:
Issuance of Class B common stock to affiliates for Major Energy Companies acquisition	0		40,000		0
Censtar and Oasis
Cash flows from investing activities:
Acquisitions	0		0		(39,847)
Provider Companies and Major Energy Companies
Cash flows from investing activities:
Acquisitions	(1,853)		(31,641)		0
Non-cash items:
Contingent consideration—earnout obligations incurred in connection with the Provider Companies and Major Energy Companies acquisitions	0		18,936		0
CenStar Earnout
Cash flows from investing activities:
Payment of earnout	0		(1,343)		0
Major Energy Companies
Cash flows from investing activities:
Payment of earnout	(7,403)		0		0
Provider Companies
Cash flows from investing activities:
Payment of earnout	(5,500)		0		0
Non-cash items:
Installment consideration incurred in connection with the acquisitions	0		1,890		0
Verde Companies
Non-cash items:
Installment consideration incurred in connection with the acquisitions	$ 19,994		$ 0		$ 0
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[4]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[5]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[6]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[7]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.
[8]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[9]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Formation and Organization

Formation and Organization	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Formation and Organization	1. Formation and Organization Organization Spark Energy, Inc. ("Spark Energy," “Company,” "we" or "us") is an independent retail energy services company that provides residential and commercial customers in competitive markets across the United States with an alternative choice for natural gas and electricity. The Company is a holding company whose sole material asset consists of units in Spark HoldCo, LLC (“Spark HoldCo”). Spark HoldCo owns all of the outstanding membership interests or common stock in each of Spark Energy, LLC (“SE”), Spark Energy Gas, LLC (“SEG”), Oasis Power Holdings, LLC ("Oasis"), CenStar Energy Corp. ("CenStar"), Electricity Maine, LLC, Electricity N.H., LLC and Provider Power Mass, LLC (collectively, the "Provider Companies"); Major Energy Services, LLC, Major Energy Electric Services, LLC, and Respond Power, LLC (collectively, the "Major Energy Companies"), Perigee Energy, LLC ("Perigee"), and the Verde Companies (as defined below) the operating subsidiaries through which the Company operates. The Company is the sole managing member of Spark HoldCo, is responsible for all operational, management and administrative decisions relating to Spark HoldCo’s business and consolidates the financial results of Spark HoldCo and its subsidiaries. Relationship with our Founder and Majority Shareholder W. Keith Maxwell, III (our "Founder") is the owner of a majority in voting power of our common stock through his ownership of NuDevco Retail, LLC ("NuDevco Retail") and Retailco, LLC ("Retailco"). Retailco is a wholly owned subsidiary of TxEx Energy Investments, LLC ("TxEx"), which is wholly owned by Mr. Maxwell. NuDevco Retail is a wholly owned subsidiary of NuDevco Retail Holdings LLC ("NuDevco Retail Holdings"), which is a wholly owned subsidiary of Electric HoldCo, LLC, which is also a wholly owned subsidiary of TxEx. We entered into a Master Service Agreement effective January 1, 2016 with Retailco Services, LLC, which is wholly owned by W. Keith Maxwell III. See Note 14 "Transactions with Affiliates" for further discussion. Emerging Growth Company Status As a company with less than $1.07 billion in revenues during its last fiscal year, the Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act. An emerging growth company may take advantage of specified reduced reporting and other regulatory requirements. The Company will remain an “emerging growth company” until as late as the last day of the Company's 2019 fiscal year, or until the earliest of (i) the last day of the fiscal year in which the Company has $1.07 billion or more in annual revenues; (ii) the date on which the Company becomes a “large accelerated filer” (the fiscal year-end on which the total market value of the Company’s common equity securities held by non-affiliates is $700 million or more as of June 30); (iii) the date on which the Company issues more than $1.0 billion of non-convertible debt over a three -year period. As a result of the Company's election to avail itself of certain provisions of the JOBS Act, the information that the Company provides may be different than what you may receive from other public companies in which you hold an equity interest. Exchange and Registration Rights The Spark HoldCo Third Amended and Restated Limited Liability Company Agreement provides that if the Company issues a new share of Class A common stock, par value $0.01 per share (the "Class A common stock"), Series A Preferred Stock (as defined below), or other equity security of the Company (other than shares of Class B common stock, par value $0.01 per share ("Class B common stock"), and excluding issuances of Class A common stock upon an exchange of Class B common stock or Series A Preferred Stock), Spark HoldCo will concurrently issue a corresponding limited liability company unit either to the holder of the Class B common stock, or to the Company in the case of the issuance of shares of Class A common stock, Series A Preferred Stock or such other equity security. As a result, the number of Spark HoldCo units held by the Company always equals the number of shares of Class A common stock, Series A Preferred Stock or such other equity securities of the Company outstanding. Each share of Class B common stock, all of which are held by NuDevco Retail and Retailco, has no economic rights but entitles the holder to one vote on all matters to be voted on by stockholders generally. Holders of Class A common stock and Class B common stock vote together as a single class on all matters presented to our stockholders for their vote or approval, except as otherwise required by applicable law or by our certificate of incorporation. NuDevco Retail and Retailco have the right to exchange (the “Exchange Right”) all or a portion of their Spark HoldCo units (together with a corresponding number of shares of Class B common stock) for Class A common stock (or cash at Spark Energy, Inc.’s or Spark HoldCo’s election (the “Cash Option”)) at an exchange ratio of one share of Class A common stock for each Spark HoldCo unit (and corresponding share of Class B common stock) exchanged. In addition, NuDevco Retail and Retailco have the right, under certain circumstances, to cause the Company to register the offer and resale of NuDevco Retail's and Retailco's shares of Class A common stock obtained pursuant to the Exchange Right. Retail Acquisition Co., LLC ("RAC") was entitled to similar registration rights under the $2.1 million convertible subordinated note (the "CenStar Note") and $5.0 million convertible subordinated note (the "Oasis Note") prior to their respective conversions to Class B common stock in January 2017. Refer to Note 8 "Debt" for further information. Tax Receivable Agreement The Company is party to a Tax Receivable Agreement with Spark HoldCo, NuDevco Retail Holdings and NuDevco Retail. This agreement generally provides for the payment by the Company to Retailco, LLC (as successor to NuDevco Retail Holdings) and NuDevco Retail of 85% of the net cash savings, if any, in U.S. federal, state and local income tax or franchise tax that the Company actually realizes (or is deemed to realize in certain circumstances) in future periods as a result of (i) any tax basis increases resulting from the purchase by the Company of Spark HoldCo units from NuDevco Retail Holdings, (ii) any tax basis increases resulting from the exchange of Spark HoldCo units for shares of Class A common stock pursuant to the Exchange Right (or resulting from an exchange of Spark HoldCo units for cash pursuant to the Cash Option) and (iii) any imputed interest deemed to be paid by the Company as a result of, and additional tax basis arising from, any payments the Company makes under the Tax Receivable Agreement. The Company retains the benefit of the remaining 15% of these tax savings. See Note 12 "Income Taxes" for further discussion. In certain circumstances, the Company may defer or partially defer any payment due (a “TRA Payment”) to the holders of rights under the Tax Receivable Agreement, which are currently Retailco and NuDevco Retail. During the five -year period ending September 30, 2019, the Company will defer all or a portion of any TRA Payment owed pursuant to the Tax Receivable Agreement to the extent that Spark HoldCo does not generate sufficient Cash Available for Distribution (as defined below) during the four -quarter period ending September 30th of the applicable year in which the TRA Payment is to be made in an amount that equals or exceeds 130% (the “TRA Coverage Ratio”) of the Total Distributions (as defined below) paid in such four-quarter period by Spark HoldCo. For purposes of computing the TRA Coverage Ratio: • “Cash Available for Distribution” is generally defined as the Adjusted EBITDA of Spark HoldCo for the applicable period, less (i) cash interest paid by Spark HoldCo, (ii) capital expenditures of Spark HoldCo (exclusive of customer acquisition costs) and (iii) any taxes payable by Spark HoldCo; and • “Total Distributions” are defined as the aggregate distributions necessary to cause the Company to receive distributions of cash equal to (i) the targeted quarterly distribution the Company intends to pay to holders of its Class A common stock and Series A Preferred Stock payable during the applicable four-quarter period, plus (ii) the estimated taxes payable by the Company during such four-quarter period, plus (iii) the expected TRA Payment payable during the calendar year for which the TRA Coverage Ratio is being tested. In the event that the TRA Coverage Ratio is not satisfied in any calendar year, the Company will defer all or a portion of the TRA Payment to NuDevco Retail or Retailco under the Tax Receivable Agreement to the extent necessary to permit Spark HoldCo to satisfy the TRA Coverage Ratio (and Spark HoldCo is not required to make and will not make the pro rata distributions to its members with respect to the deferred portion of the TRA Payment). If the TRA Coverage Ratio is satisfied in any calendar year, the Company will pay NuDevco Retail or Retailco the full amount of the TRA Payment. Following the five -year deferral period ending September 30, 2019, the Company will be obligated to pay any outstanding deferred TRA Payments to the extent such deferred TRA Payments do not exceed (i) the lesser of the Company's proportionate share of aggregate Cash Available for Distribution of Spark HoldCo during the five -year deferral period or the cash distributions actually received by the Company during the five -year deferral period, reduced by (ii) the sum of (a) the aggregate target quarterly dividends (which, for the purposes of the Tax Receivable Agreement, will be $0.18125 per Class A common stock share and $0.546875 per Series A Preferred Stock share per quarter) during the five -year deferral period, (b) the Company's estimated taxes during the five -year deferral period, and (c) all prior TRA Payments and (d) if with respect to the quarterly period during which the deferred TRA Payment is otherwise paid or payable, Spark HoldCo has or reasonably determines it will have amounts necessary to cause the Company to receive distributions of cash equal to the target quarterly distribution payable during that quarterly period. Any portion of the deferred TRA Payments not payable due to these limitations will no longer be payable. We met the threshold coverage ratio required to fund the second TRA Payment to Retailco and NuDevco Retail under the Tax Receivable Agreement during the four-quarter period ending September 30, 2016, resulting in an initial TRA Payment of $1.4 million becoming due in December 2016. On November 6, 2016, Retailco and NuDevco Retail granted the Company the right to defer the TRA Payment until May 2018. During the period of time when the Company has elected to defer the TRA Payment, the outstanding payment amount will accrue interest at a rate calculated in the manner provided for under the Tax Receivable Agreement. The initial payment of $1.4 million deferred until May 2018 was classified to a current liability as of December 31, 2017 . We met the threshold coverage ratio required to fund the third TRA Payment to Retailco and NuDevco Retail under the Tax Receivable Agreement during the four-quarter periods ending September 30, 2017. As such, the third payment under the Tax Receivable Agreement due in April 2018 has been classified as current in our consolidated balance sheet at December 31, 2017 . We expect to meet the threshold coverage ratio required to fund the fourth payment to Retailco and NuDevco Retail under the Tax Receivable Agreement during the four-quarter period ending September 30, 2018. As such, the fourth payment under the Tax Receivable Agreement due in late 2018 has been classified as current in our consolidated balance sheet at December 31, 2017 .

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	2. Basis of Presentation and Summary of Significant Accounting Policies The accompanying consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). The Company's consolidated financial statements are presented on a consolidated basis and include all wholly-owned and controlled subsidiaries. We account for investments over which we have significant influence but not a controlling financial interest using the equity method of accounting. All significant intercompany transactions and balances have been eliminated in the consolidated financial statements. Transactions with Affiliates The Company enters into transactions with and pays certain costs on behalf of affiliates that are commonly controlled by W. Keith Maxwell III, and these affiliates enter into transactions with and pay certain costs on our behalf, in order to reduce risk, reduce administrative expense, create economies of scale, create strategic alliances and supply goods and services among these related parties. These transactions include, but are not limited to, certain services to the affiliated companies associated with employee benefits provided through the Company’s benefit plans, insurance plans, leased office space, administrative salaries for management due diligence work, recurring management consulting, and accounting, tax, legal, or technology services based on services provided, departmental usage, or headcount, which are considered reasonable by management. As such, the accompanying consolidated financial statements include costs that have been incurred by the Company and then directly billed or allocated to affiliates, and costs that have been incurred by our affiliates and then directly billed or allocated to us, and are recorded net in general and administrative expense on the consolidated statements of operations with a corresponding accounts receivable—affiliates or accounts payable—affiliates, respectively, recorded in the consolidated balance sheets. Additionally, the Company enters into transactions with certain affiliates for sales or purchases of natural gas and electricity, which are recorded in retail revenues, retail cost of revenues, and net asset optimization revenues in the consolidated statements of operations with a corresponding accounts receivable—affiliate or accounts payable—affiliate in the consolidated balance sheets. The allocations and related estimates and assumptions are described more fully in Note 14 "Transactions with Affiliates." Cash and Cash Equivalents Cash and cash equivalents consist of all unrestricted demand deposits and funds invested in highly liquid instruments with original maturities of three months or less. The Company periodically assesses the financial condition of the institutions where these funds are held and believes that its credit risk is minimal with respect to these institutions. Accounts Receivable Trade accounts receivable are recorded at the invoiced amount and do not bear interest. Accounts receivable in the consolidated balance sheets are net of allowance for doubtful accounts of $4.0 million and $2.3 million as of December 31, 2017 and 2016 , respectively. The Company accrues an allowance for doubtful accounts based upon estimated uncollectible accounts receivable considering historical collections, accounts receivable aging analysis, credit risk and other factors. The Company writes off accounts receivable balances against the allowance for doubtful accounts when the accounts receivable is deemed to be uncollectible. Bad debt expense of $6.6 million , $1.3 million and $7.9 million was recorded in general and administrative expense in the consolidated statements of operations for the years ended December 31, 2017 , 2016 and 2015 , respectively. The Company conducts business in many utility service markets where the local regulated utility purchases our receivables, and then becomes responsible for billing the customer and collecting payment from the customer (“POR programs”). This POR service results in substantially all of the Company’s credit risk being linked to the applicable utility, which generally has an investment-grade rating, and not to the end-use customer. The Company monitors the financial condition of each utility and currently believes that its susceptibility to an individually significant write-off as a result of concentrations of customer accounts receivable with those utilities is remote. Trade accounts receivable that are part of a local regulated utility’s POR program are recorded on a gross basis in accounts receivable in the consolidated balance sheets. The discount paid to the local regulated utilities is recorded in general and administrative expense in the consolidated statements of operations. In markets that do not offer POR services or when the Company chooses to directly bill its customers, certain receivables are billed and collected by the Company. The Company bears the credit risk on these accounts and records an appropriate allowance for doubtful accounts to reflect any losses due to non-payment by customers. The Company’s customers are individually insignificant and geographically dispersed in these markets. The Company writes off customer balances when it believes that amounts are no longer collectible and when it has exhausted all means to collect these receivables. Inventory Inventory consists of natural gas used to fulfill and manage seasonality for fixed and variable-price retail customer load requirements and is valued at the lower of weighted average cost or market. Purchased natural gas costs are recognized in the consolidated statements of operations, within retail cost of revenues, when the natural gas is sold and delivered out of the storage facility. There were no inventory impairments recorded for the years ended December 31, 2017 , 2016 and 2015 . When natural gas is sold costs are recognized in the consolidated statements of operations, within retail cost of revenues, at the weighted average cost value at the time of the sale. Customer Acquisition Costs The Company has retail natural gas and electricity customer acquisition costs, net of $22.1 million and $18.8 million recorded in current assets and $6.9 million and $6.1 million recorded in noncurrent assets representing direct response advertising costs as of December 31, 2017 and 2016 , respectively. Customer acquisition costs are spending for organic customer acquisitions and do not include customer acquisitions through merger and acquisition activities, which are recorded as customer relationships. Amortization of customer acquisition costs, recorded in depreciation and amortization in the consolidated statements of operations, was $21.4 million , $17.5 million and $18.0 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Capitalized direct response advertising costs consist primarily of hourly and commission based telemarketing costs, door-to-door agent commissions and other direct advertising costs associated with proven customer generation, and are capitalized and amortized over the estimated two -year average life of a customer in accordance with the provisions of FASB ASC 340-20, Capitalized Advertising Costs . Recoverability of customer acquisition costs is evaluated based on a comparison of the carrying amount of the customer acquisition costs to the future net cash flows expected to be generated by the customers acquired, considering specific assumptions for customer attrition, per unit gross profit, and operating costs. These assumptions are based on forecasts and historical experience. Customer Relationships Customer acquisitions through direct acquisitions of customer contracts or recorded as part of the acquisition method in accordance with FASB ASC Topic 805, Business Combinations ("ASC 805") are recorded as customer relationships and represent customer contract acquisitions not acquired through the direct response advertising discussed above at “ Customer Acquisition Costs. ” The Company has recorded $18.7 million and $12.1 million , net of amortization, as current assets as of December 31, 2017 and 2016 , respectively, and $34.8 million and $21.4 million , net of amortization, as non-current assets as of December 31, 2017 and 2016 , respectively, related to these intangible assets. These intangibles are amortized on a straight-line basis over the estimated average life of the related customer contracts acquired, which ranges from three years to six years . The acquired customer relationships intangibles related to Oasis, CenStar, Provider Companies, Major Energy Companies, Perigee Energy LLC, and Verde Companies are reflective of the acquired companies’ customer base, and were valued at the respective dates of acquisition using an excess earnings method under the income approach. Using this method, the Company estimated the future cash flows resulting from the existing customer relationships, considering attrition as well as charges for contributory assets, such as net working capital, fixed assets, and assembled workforce. These future cash flows were then discounted using an appropriate risk-adjusted rate of return by retail unit to arrive at the present value of the expected future cash flows. CenStar, Oasis and Perigee customer relationships are amortized to depreciation and amortization based on the expected future net cash flows by year. The acquired customer relationship intangibles related to the Major Energy Companies, the Provider Companies and the Verde Companies were bifurcated between hedged and unhedged and amortized to depreciation and amortization based on the expected future cash flows by year and expensed to retail cost of revenue based on the expected term of the underlying fixed price contract in each reporting period, respectively. Amortization expense was $17.8 million , $28.6 million , and $5.7 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Approximately $0.3 million , $15.8 million , and zero of the $17.8 million , $28.6 million , and $5.7 million customer relationships amortization expense for the twelve months ending December 31, 2017 , 2016 , and 2015 , respectively, was included in retail cost of revenue. We review customer relationships for impairment whenever events or changes in business circumstances indicate the carrying value of the intangible assets may not be recoverable. Impairment is indicated when the undiscounted cash flows estimated to be generated by the intangible assets are less than their respective carrying value. If an impairment exists, a loss would be recognized for the difference between the fair value and carrying value of the intangible assets. No impairments of customer relationships were recorded for the years ended December 31, 2017 , 2016 and 2015 . Non-compete agreements The non-compete agreements provide the Company with a certain level of assurance that acquired companies' expected earnings streams will not be disrupted by competition from the companies’ previous members. The fair values of non-compete agreements are determined using the differential valuation approach at acquisition date. Under this approach, the Company estimates the present value of expected future cash flows under two scenarios; one scenario assumes the non-compete agreements are in place and the other scenario assumes the absence of non-compete agreements. The resulting difference between the two scenarios is the implied value of the non-compete agreements, which is further adjusted by an estimated probability factor representing the likelihood that previous members of acquired companies would be successful competitors. As a result of the Provider Companies and Major Energy Companies acquisitions, the Company recorded $1.2 million , net of amortization, as Acquired customer intangibles - current and $1.4 million , net of amortization, as Acquired customer intangibles - non-current as of December 31, 2016 related to these non-compete agreements. These non-compete agreements are amortized over their estimated three -year life on a straight-line basis. Amortization expense was $1.2 million and $0.9 million for the years ended December 31, 2017 and 2016 . Trademarks Trademarks recorded as part of the acquisition method in accordance with ASC 805 represent the value associated with the recognition and positive reputation of an acquired company to its target markets. This value would otherwise have to be internally developed through significant time and expense or by paying a third party for its use. The fair values of trademark assets were determined at the date of acquisition using a royalty savings method under the income approach. Under this approach, the Company estimates the present value of expected cash flows resulting from avoiding royalty payments to use a third party trademark. The Company analyzes market royalty rates charged for licensing trademarks and applied an expected royalty rate to a forecast of estimated revenue, which was then discounted using an appropriate risk adjusted rate of return. The Company has recorded $8.6 million and $6.3 million , net of amortization, as other assets as of December 31, 2017 and 2016 related to these trademarks in other assets. These intangibles are amortized over the estimated five -year to twenty -year life of the trademarks on a straight-line basis. Amortization expense was $0.8 million , $0.4 million and $0.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. We review trademarks for impairment whenever events or changes in business circumstances indicate the carrying value of the intangible assets may not be recoverable. Impairment is indicated when the undiscounted cash flows estimated to be generated by the intangible assets are less than their respective carrying value. If an impairment exists, a loss would be recognized for the difference between the fair value and carrying value of the intangible assets. No impairments of trademarks were recorded for the years ended December 31, 2017 , 2016 and 2015 . Deferred Financing Costs Costs incurred in connection with the issuance of long-term debt are capitalized and amortized to interest expense using the straight-line method over the life of the related long-term debt due to the variable nature of the Company’s long-term debt. Property and Equipment The Company records property and equipment at historical cost. Depreciation expense is recorded on a straight-line method based on estimated useful lives. When assets are placed into service, management makes estimates with respect to useful lives and salvage values of the assets. When items of property and equipment are sold or otherwise disposed of, any gain or loss is recorded in the consolidated statements of operations. The Company capitalizes costs associated with internal-use software projects in accordance with FASB ASC Topic 350-40, Internal-Use Software . Capitalized costs are the costs incurred during the application development stage of the internal-use software project such as software configuration, coding, installation of hardware and testing. Costs incurred during the preliminary or post-implementation stage of the internal-use software project are expensed in the period incurred. These types of costs include formulation of ideas and alternatives, training and application maintenance. After internal-use software projects are completed, the associated capitalized costs are depreciated over the estimated useful life of the related asset. Interest costs incurred while developing internal-use software projects are capitalized in accordance with FASB ASC Topic 835-20, Capitalization of Interest . Capitalized interest costs for the years ended December 31, 2017 , 2016 and 2015 were not material. Goodwill Goodwill represents the excess of cost over fair value of the assets of businesses acquired in accordance with FASB ASC Topic 350 Intangibles-Goodwill and Other ("ASC 350"). The goodwill on our consolidated balance sheet as of December 31, 2017 is associated with both our Retail Natural Gas and Retail Electricity reporting units. We determine our reporting units by identifying each unit that engaged in business activities from which it may earn revenues and incur expenses, had operating results regularly reviewed by the segment manager for purposes of resource allocation and performance assessment, and had discrete financial information. Goodwill is assessed for impairment whenever events or circumstances indicate that impairment of the carrying value of goodwill is likely, but no less often than annually as of October 31. On October 31, 2017, we elected to by-pass the option to perform a qualitative assessment of goodwill and performed a quantitative assessment of goodwill in accordance with guidance from ASC 350. This guidance permits an entity to first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment test. If we fail the qualitative test or if we elect to by-pass the qualitative assessment, then we must compare our estimate of the fair value of a reporting unit with its carrying value, including goodwill. If the carrying value of the reporting unit exceeds its fair value, we perform the second step of the goodwill impairment test to measure the amount of goodwill impairment loss to be recorded, as necessary. The second step compares the implied fair value of the reporting unit’s goodwill to the carrying value, if any, of that goodwill. We determine the implied fair value of the goodwill in the same manner as determining the amount of goodwill to be recognized in a business combination. The inputs used in the determination of fair value are generally level 3 inputs. See Note 9 "Fair Value Measurements" for further discussion. We completed our annual assessment of goodwill impairment as of October 31, 2017 during the fourth quarter of 2017, and the test indicated no impairment. Treasury Stock Treasury stock consists of Company's own stock that has been issued, but is subsequently reacquired by the Company. Treasury stock does not reduce the number of shares issued but does reduce the number of shares outstanding. These shares are not eligible to receive cash dividends. Accounting for treasury stock transactions is governed by FASB ASC Topic 550-30 Equity-Treasury Stock. We use the cost method to account for treasury shares. Purchases of shares of Class A common stock are recorded at cost, and the gross cost of the Class A common stock purchased is charged to a contra equity account entitled "Treasury Stock." Equity Method Investment The Company accounts for investments in unconsolidated entities using the equity method of accounting, as prescribed in FASB ASC Topic 323-10, Investments-Equity Method and Joint Venture, if the investment gives us the ability to exercise significant influence over, but not control, of an investee. Significant influence generally exists if we have an ownership interest representing between 20% and 50% of the voting stock of the investee. Under the equity method of accounting, investments are stated at initial cost and are adjusted for subsequent additional investments and our proportionate share of earnings or losses and distributions. Such investment is presented on the consolidated balance sheet under "Other assets" and our share of their income as "Interest and other income" on the consolidated statements of operations. The Company determines its equity investment earnings using the Hypothetical Liquidation at Book Value (HLBV) method. Under the HLBV method, a calculation is prepared at each balance sheet date to determine the amount the Company would receive if the investee were to liquidate all of its assets, as valued in accordance with U.S. GAAP, and distribute that cash to the investors. The difference between the calculated liquidation distribution amounts at the beginning and the end of the reporting period, after adjusting for capital contributions and distributions, is the Company's share of the earnings or losses from the equity investment for the period. See Note 17 "Equity Method Investment" for further discussion. Segment Reporting The FASB ASC Topic 280, Segment Reporting , established standards for entities to report information about the operating segments and geographic areas in which they operate. The Company operates two segments, retail natural gas and retail electricity, and all of its operations are located in the United States. Revenues and Cost of Revenues The Company’s revenues are derived primarily from the sale of natural gas and electricity to retail customers. The Company also records revenue from sales of natural gas and electricity to wholesale counterparties, including affiliates. Revenues are recognized by the Company using the following criteria: (1) persuasive evidence of an exchange arrangement exists, (2) delivery has occurred or services have been rendered, (3) the buyer’s price is fixed or determinable and (4) collection is reasonably assured. Utilizing these criteria, revenue is recognized when the natural gas or electricity is delivered. Similarly, cost of revenues is recognized when the commodity is delivered. Revenues for natural gas and electricity sales are recognized upon delivery under the accrual method. Natural gas and electricity sales that have been delivered but not billed by period end are estimated. Accrued unbilled revenues are based on estimates of customer usage since the date of the last meter read provided by the utility. Volume estimates are based on forecasted volumes and estimated customer usage by class. Unbilled revenues are calculated by multiplying these volume estimates by the applicable rate by customer class. Estimated amounts are adjusted when actual usage is known and billed. The Company records gross receipts taxes on a gross basis in retail revenues and retail cost of revenues. During the years ended December 31, 2017 , 2016 and 2015 , the Company’s retail revenues and retail cost of revenues included gross receipts taxes of $9.0 million , $5.3 million and $3.0 million , respectively. Costs for natural gas and electricity sales are recognized as the commodity is delivered to the customer under the accrual method. Natural gas and electricity costs that have not been billed to the Company by suppliers but have been incurred by period end are estimated. The Company estimates volumes for natural gas and electricity delivered based on the forecasted revenue volumes, estimated transportation cost volumes and estimation of other costs associated with retail load that varies by commodity utility territory. These costs include items like ISO fees, ancillary services and renewable energy credits. Estimated amounts are adjusted when actual usage is known and billed. The Company’s asset optimization activities, which primarily include natural gas physical arbitrage and other short term storage and transportation opportunities, meet the definition of trading activities and are recorded on a net basis in the consolidated statements of operations in net asset optimization revenues pursuant to FASB ASC Topic 815, Derivatives and Hedging . The Company recorded asset optimization revenues, primarily related to physical sales or purchases of commodities, of $178.3 million , $133.0 million and $154.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, and recorded asset optimization costs of revenues of $179.0 million , $133.6 million and $152.6 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, which are presented on a net basis in asset optimization revenues. Natural Gas Imbalances The consolidated balance sheets include natural gas imbalance receivables and payables, which primarily results when customers consume more or less gas than has been delivered by the Company to local distribution companies (“LDCs”). The settlement of natural gas imbalances varies by LDC, but typically the natural gas imbalances are settled in cash or in kind on a monthly, quarterly, semi-annual or annual basis. The imbalances are valued at an estimated net realizable value. The Company recorded an imbalance receivable of $0.7 million and $0.9 million recorded in other current assets on the consolidated balance sheets as of December 31, 2017 and 2016 , respectively. The Company recorded an imbalance payable of $1.0 million and $0.1 million recorded in other current liabilities on the consolidated balance sheets as of December 31, 2017 and 2016 , respectively. Fair Value FASB ASC Topic 820, Fair Value Measurement , established a single authoritative definition of fair value, set out a framework for measuring fair value, and requires disclosures about fair value measurements. The standard clarifies that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. The standard utilizes a fair value hierarchy that prioritizes the inputs to the valuation techniques used to measure fair value into three broad levels based on quoted prices in active market, observable market prices, and unobservable market prices. When the Company is required to measure fair value, and there is not a quoted or observable market price for a similar asset or liability, the Company utilizes the cost, income, or market valuation approach depending on the quality of information available to support management’s assumptions. Derivative Instruments The Company uses derivative instruments such as futures, swaps, forwards and options to manage the commodity price risks of its business operations. All derivatives, other than those for which an exception applies, are recorded in the consolidated balance sheets at fair value. Derivative instruments representing unrealized gains are reported as derivative assets while derivative instruments representing unrealized losses are reported as derivative liabilities. The Company has elected to offset amounts in the consolidated balance sheets for derivative instruments executed with the same counterparty under a master netting arrangement. One of the exceptions to fair value accounting, normal purchases and normal sales, has been elected by the Company for certain derivative instruments when the contract satisfies certain criteria, including a requirement that physical delivery of the underlying commodity is probable and is expected to be used in normal course of business. Retail revenues and retail cost of revenues resulting from deliveries of commodities under normal purchase contracts and normal sales contracts are included in earnings at the time of contract settlement. To manage commodity price risk, the Company holds certain derivative instruments that are not held for trading purposes and are not designated as hedges for accounting purposes. However, to the extent the Company does not hold offsetting positions for such derivatives, they believe these instruments represent economic hedges that mitigate their exposure to fluctuations in commodity prices. As part of the Company’s strategy to optimize its assets and manage related commodity risks, it also manages a portfolio of commodity derivative instruments held for trading purposes. The Company uses established policies and procedures to manage the risks associated with price fluctuations in these energy commodities and uses derivative instruments to reduce risk by generally creating offsetting market positions. Changes in the fair value of and amounts realized upon settlement of derivative instruments not held for trading purposes are recognized currently in retail costs of revenues. Changes in the fair value of and amounts realized upon settlement of derivative instruments held for trading purposes are recognized currently in earnings in net asset optimization revenues. Income Taxes The Company recognizes the amount of taxes payable or refundable for the year. In addition, the Company follows the asset and liability method of accounting for income taxes where deferred tax assets and liabilities are recognized for the expected future tax consequences of events that have been recognized in the financial statements or tax returns and operating loss carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in those years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in the tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is provided for deferred tax assets if it is more likely than not that these items will not be realized. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the projected future taxable income and tax planning strategies in making this assessment. Based upon the level of historical taxable income and projections for future taxable income over the periods in which the deferred tax assets are deductible, management believes it is more likely than not that we will realize the benefits of these deductible differences. The Company recognizes interest and penalties related to unrecognized tax benefits within the provision for income taxes on continuing operations in our consolidated statements of operations. Earnings per Share Basic earnings per share (“EPS”) is computed by dividing net income attributable to shareholders (the numerator) by the weighted-average number of Class A common shares outstanding for the period (the denominator). Class B common shares are not included in the calculation of basic earnings per share because they are not participating securities and have no economic interest in the Company. Diluted earnings per share is similarly calculated except that the denominator is increased (1) using the treasury stock method to determine the potential dilutive effect of the Company’s outstanding unvested restricted stock units, (2) using the if-converted method to determine the potential dilutive effect of the Company’s Class B common stock and (3) using the if-converted method to determine the potential dilutive effect of the outstanding convertible subordinated notes into the Company's Class B common stock. On May 22, 2017, the Company authorized and approved a two -for-one stock split of the Company's issued Class A common stock and Class B common stock, which was effected through a stock dividend (the "Stock Split"). All shares and per share amounts in this report have been retrospectively restated to reflect the Stock Split. Non-controlling Interest The Company and NuDevco Retail and Retailco owned the following economic interests in Spark HoldCo at December 31, 2016 and December 31, 2017 , respectively. The Company NuDevco Retail and Retailco (1) (2) On December 31, 2016 38.85% 61.15% On December 31, 2017 38.12% 61.88% (1) In January 2016, Retailco succeeded to the interest of NuDevco Retail Holdings of its Class B common stock and an equal number of Spark HoldCo units it held pursuant to a series of transfers. (2) In January 2017, Retailco converted the CenStar Note and Oasis Note to 269,462 and 766,180 shares, respectively, of Class B common stock. See Note 4 "Equity" for further detail. Net income attributable to non-controlling interest for the years ended December 31, 2017 and 2016 represents NuDevco’s interest in Spark HoldCo. Income and expenses specifically attributable to the non-controlling interest and the Company are allocated accordingly (for example income tax expense (benefit), gain related to the remeasurement of the TRA liability as a result of U.S. Tax Reform, and income (loss) related to recast financial statements). The weighted average ownership percentages for the applicable reporting period are used to allocate the remaining income (loss) before income taxes to the each economic interest owner. Commitments and Contingencies The Company enters into variou

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	3. Acquisitions Acquisition of CenStar Energy Corp On July 8, 2015, the Company completed its acquisition of CenStar, a retail energy company based in New York. CenStar serves natural gas and electricity customers in New York, New Jersey, and Ohio. The purchase price for the CenStar acquisition was $8.3 million , subject to working capital adjustments, plus a payment for positive working capital of $10.4 million and an earnout payment estimated as of the acquisition date to be $0.5 million , which was associated with a financial measurement attributable to the operations of CenStar for the year following the closing ("CenStar Earnout"). See Note 9 "Fair Value Measurements" for further discussion of the CenStar Earnout. The purchase price was financed with $16.6 million (including positive working capital of $10.4 million ) under our Senior Credit Facility and $2.1 million from the issuance of a convertible subordinated note ("CenStar Note") from the Company and Spark HoldCo to Retailco Acquisition Co, LLC ("RAC"). See Note 8 "Debt" for further discussion of the Senior Credit Facility and the CenStar Note. The Company’s consolidated statements of operations for the year ended December 31, 2015 included $21.4 million of revenue and a $1.4 million loss on operations of CenStar. The Company incurred $0.1 million of acquisition related costs for the year ended December 31, 2015, in connection with the acquisition of CenStar, which have been expensed as incurred and included in general and administrative expense in the consolidated statement of operations. Acquisition of Oasis Power Holdings, LLC On July 31, 2015, the Company completed its acquisition of Oasis, a retail energy company operating in six states across 18 utilities. The purchase price for the Oasis acquisition was $20.0 million , subject to working capital adjustments. The purchase price was financed with $15.0 million in borrowings under our Senior Credit Facility, $5.0 million from the issuance of a convertible subordinated note ("Oasis Note") from the Company and Spark HoldCo to RAC, and $2.0 million cash on hand. See Note 8 "Debt" for further discussion of the Senior Credit Facility and the Oasis Note. The acquisition of Oasis by the Company from RAC was a transfer of equity interests of entities under common control on July 31, 2015. The Company’s consolidated statements of operations for year ended December 31, 2015 included $26.9 million of revenue and a $0.5 million loss on the operations of Oasis. Acquisition of the Provider Companies On August 1, 2016, the Company and Spark HoldCo completed the purchase of all of the outstanding membership interests of the Provider Companies. The Provider Companies serve electrical customers in Maine, New Hampshire and Massachusetts. The purchase price for the Provider Companies was approximately $34.1 million , which included $1.3 million in working capital, subject to adjustments, and up to $9.0 million in earnout payments, valued at $4.8 million as of the purchase date, which was to be paid by June 30, 2017, subject to the achievement of certain performance targets (the "Provider Earnout"). See Note 9 "Fair Value Measurements" for further discussion on the Provider Earnout, including the final earnout payment made in June 2017. The purchase price was funded by the sale of 1,399,484 shares of Class B common stock (and a corresponding number of Spark HoldCo units) to Retailco, valued at $14.0 million based on a value of $10 per share; borrowings under the Senior Credit Facility of $10.6 million ; and $3.8 million in net installment consideration to be paid in ten monthly payments that commenced in August 2016. The first payment of the installment consideration in the amount of $0.4 million was made with the initial consideration paid. See Note 8 "Debt" for further discussion of the Senior Credit Facility. The acquisition of the Provider Companies was accounted for under the acquisition method in accordance with ASC 805, Business Combinations (“ASC 805”). The allocation of purchase consideration was based upon the estimated fair value of the tangible and identifiable intangible assets acquired and liabilities assumed in the acquisition. The allocation was made to major categories of assets and liabilities based on management’s best estimates, and supported by independent third-party analyses. The excess of the purchase price over the estimated fair value of tangible and intangible assets acquired and liabilities assumed was allocated to goodwill. The purchase price allocation for the acquisition of the Provider Companies was finalized as of December 31, 2016. The allocation of the purchase consideration is as follows (in thousands): Final as of December 31, 2016 Cash $ 431 Net working capital, net of cash acquired 812 Intangible assets - customer relationships and non-compete agreements 24,417 Intangible assets - trademark 529 Goodwill 26,040 Fair value of derivative liabilities (18,163 ) Total $ 34,066 The fair values of intangible assets were measured primarily based on significant inputs that are not observable in the market and thus represent a Level 3 measurement as defined by ASC 820, Fair Value Measurement ("ASC 820"). The fair value of derivative liabilities were measured by utilizing readily available quoted market prices and non-exchange-traded contracts fair valued using market price quotations available through brokers or over-the-counter and on-line exchanges and represent a Level 2 measurement as defined by ASC 820. Refer to Note 9 "Fair Value Measurements" for further discussion on the fair values hierarchy. Significant inputs for Level 3 measurements related to customer relationships, non-compete agreements and trademarks are discussed in Note 2 "Basis of Presentation and Summary of Significant Accounting Policies." Significant inputs for Level 3 measurements related to goodwill were as follows: Goodwill The excess of the purchase consideration over the estimated fair value of the amounts initially assigned to the identifiable assets acquired and liabilities assumed was recorded as goodwill. Goodwill arose on the acquisition of the Provider Companies primarily due the value of its assembled workforce, along with access to new utility service territories. Goodwill recorded in connection with the acquisition of the Provider Companies is deductible for income tax purposes because the Provider Companies was an acquisition of all of the assets of the Provider Companies. The valuation and purchase price allocation of the Provider Companies was based on a preliminary fair value analysis. Prior to the measurement period's expiration, the Company recorded adjustments to the working capital balances upon settlement of the final working capital balances per the terms of the purchase agreement. The Company’s consolidated statements of operations for the year ended December 31, 2016, respectively, included $46.8 million of revenue and $12.8 million of losses from operations related to the operations of the Provider Companies. We have not included pro forma information for the Provider Companies acquisition because it did not have a material impact on our financial position or results of operations. Acquisition of the Major Energy Companies On August 23, 2016, the Company and Spark HoldCo completed the purchase of all of the outstanding membership interests of the Major Energy Companies, which are retail energy companies operating in Connecticut, Illinois, Maryland (including the District of Columbia), Massachusetts, New Jersey, New York, Ohio, and Pennsylvania across 43 utilities, from NG&E in exchange for consideration of $64.1 million , which included $5.2 million in working capital; an assumed litigation reserve of $5.0 million , and up to $35.0 million in installment and earnout payments, valued at $13.1 million as of NG&E's April 15, 2016 purchase date, to be paid to the previous members of the Major Energy Companies, in annual installments on March 31, 2017, 2018 and 2019, subject to the achievement of certain performance targets (the “Major Earnout”). The Company is obligated to issue up to 400,000 shares of Class B common stock (and a corresponding number of Spark HoldCo units) to NG&E, subject to the achievement of certain performance targets, valued at $0.8 million ( 81,436 shares valued at $10 per share) as of the purchase date (the "Stock Earnout"). See Note 9 "Fair Value Measurements" for further discussion on the Major Earnout and Stock Earnout. The purchase price was funded by the issuance of 4,000,000 shares of Class B common stock (and a corresponding number of Spark HoldCo units) valued at $40.0 million based on a value of $10 per share, to NG&E. NG&E is owned by our Founder. The acquisition of the Major Energy Companies by the Company and Spark HoldCo from NG&E was a transfer of equity interests of entities under common control on August 23, 2016. Accordingly, the assets acquired and liabilities assumed were based on their historical values as of August 23, 2016. NG&E acquired the Major Energy Companies on April 15, 2016 and the fair value of the net assets acquired was as follows (in thousands): Reported as of December 31, 2016 2017 Adjustments (1) December 31, 2017 Cash $ 17,368 $ — $ 17,368 Property and equipment 14 — 14 Intangible assets - customer relationships & non-compete agreements 24,271 — 24,271 Other assets - trademarks 4,973 — 4,973 Non-current deferred tax assets 1,042 — 1,042 Goodwill 34,728 260 34,988 Net working capital, net of cash acquired (6,746 ) — (6,746 ) Fair value of derivative liabilities (7,260 ) — (7,260 ) Total $ 68,390 $ 260 $ 68,650 (1) Changes to the purchase price allocation during 2017 related to NG&E's working capital settlement with the Major Energy Companies' sellers. The working capital paid to Major Energy Companies by NG&E was $10.6 million . The Company paid $4.3 million in working capital to NG&E on August 23, 2016, and settled working capital with NG&E for $5.2 million in 2017. The $0.9 million related to the working capital true-up between the Company and NG&E is included in accounts payable-affiliates as of December 31, 2017. Approximately $3.9 million was recorded as an equity transaction and treated as a contribution on August 23, 2016. The Stock Earnout liability of $0.8 million due to NG&E and the working capital true-up of $0.3 million are also recorded as an equity transaction and treated as a contribution as of December 31, 2017 . The value of the Stock Earnout liability was zero as of December 31, 2017 . See further discussion in Note 9 "Fair Value Measurements." The fair values of intangible assets were measured primarily based on significant inputs that are not observable in the market and thus represent a Level 3 measurement as defined by ASC 820, Fair Value Measurement ("ASC 820"). The fair value of derivative liabilities were measured by utilizing readily available quoted market prices and non-exchange-traded contracts fair valued using market price quotations available through brokers or over-the-counter and on-line exchanges and represent a Level 2 measurement as defined by ASC 820. Refer to Note 9 "Fair Value Measurements" for further discussion on the fair values hierarchy. Significant inputs for Level 3 measurements related to customer relationships, non-compete agreements and trademarks are discussed in Note 2 "Basis of Presentation and Summary of Significant Accounting Policies." Significant inputs for Level 3 measurements related to goodwill were as follows: Goodwill The excess of the purchase consideration over the estimated fair value of the amounts initially assigned to the identifiable assets acquired and liabilities assumed was recorded as goodwill. Goodwill arose on the acquisition of the Major Energy Companies by NG&E primarily due to the value of the Major Energy Companies brand strength, established vendor relationships and access to new utility service territories. Goodwill recorded in connection with the acquisition of the Major Energy Companies is deductible for income tax purposes because the acquisition of the Major Energy Companies was an acquisition of all of the assets of the Major Energy Companies. Goodwill was transferred to the Company based on the acquisition of the Major Energy Companies by NG&E on April 15, 2016. Goodwill recorded in connection with the transfer of the Major Energy Companies is deductible for income tax purposes. In December 2016, certain executives of the Major Energy Companies exercised a change of control provision under employment agreements with the Major Energy Companies. As a result, the Company recorded employment contract termination costs of $4.1 million as of December 31, 2016. The Company paid employment contract termination costs totaling approximately $2.5 million during the year ended December 31, 2017 . As of December 31, 2017 , the Company's liability related to the contract termination costs was $1.6 million , to be paid over a 22 month period beginning April 1, 2017. The Major Energy Companies contributed revenues of $125.6 million and earnings of $1.3 million to the Company for the year ended December 31, 2016. The following unaudited pro forma revenue and earnings summary presents consolidated information of the Company as if the acquisition had occurred on January 1, 2015 (in thousands): Year Ended December 31, 2016 2015 Revenue $603,673 $547,381 Earnings $15,776 $15,460 The pro forma results are not necessarily indicative of our consolidated results of operations in future periods or the results that actually would have been realized had the companies operated on a combined basis during the periods presented. The revenue and earnings for the twelve months ended December 31, 2016 reflects actual results of operations for the period from April 15, 2016 through December 31, 2016, the period the financial results were fully combined. The pro forma results include adjustments primarily related to amortization of acquired intangibles, and certain accounting policy alignments as well as direct and incremental acquisition related costs reflected in the historical financial statements. The purchase price allocation was used to prepare the pro forma adjustments. Acquisition of Perigee On April 1, 2017, the Company and Spark Holdco completed the purchase of all of the outstanding membership interest of Perigee, a Texas limited liability company, with operations across 14 utilities in Connecticut, Delaware, Massachusetts, New York and Ohio. The purchase price for Perigee from NG&E was approximately $4.1 million , which consisted of a base price of $2.0 million , $0.2 million additional customer option payment, and $1.9 million in working capital. The acquisition of Perigee by the Company and Spark HoldCo from NG&E was a transfer of equity interests of entities under common control on April 1, 2017. Accordingly, the assets acquired and liabilities assumed were based on their historical value as of April 1, 2017. NG&E acquired Perigee on February 3, 2017 and the fair value of the net assets acquired was as follows (in thousands): As of December 31, 2017 Cash $ 23 Intangible assets - customer relationships 1,100 Goodwill 1,540 Net working capital, net of cash acquired 2,085 Fair value of derivative liabilities (443 ) Total $ 4,305 Customer relationships The acquired customer relationships intangibles related to Perigee are reflective of Perigee's customer base, and were valued at the respective dates of acquisition using an excess earnings method under the income approach. Using this method, the Company estimated the future cash flows resulting from the existing customer relationships, considering attrition as well as charges for contributory assets, such as net working capital, fixed assets, and assembled workforce. These future cash flows were then discounted using an appropriate risk-adjusted rate of return by retail unit to arrive at the present value of the expected future cash flows. These customer relationships are amortized to depreciation and amortization based on the expected future net cash flows by year. Goodwill The excess of the purchase consideration over the estimated fair value of the amounts initially assigned to the identifiable assets acquired and liabilities assumed was recorded as goodwill. Goodwill arose on the acquisition of Perigee by NG&E primarily due to the value of Perigee's access to a new utility service territory. Goodwill recorded in connection with the acquisition of Perigee is deductible for income tax purposes because the acquisition of Perigee was an acquisition of all of the assets of Perigee. The valuation and purchase price allocation of Perigee was based on a preliminary fair value analysis performed as of February 3, 2017, the date Perigee was acquired by NG&E. We have not included pro forma information for the Perigee acquisition because it did not have a material impact on our financial position or results of operations. Acquisition of Verde On July 1, 2017, the Company, through CenStar, its subsidiary, completed the acquisition from Verde Energy USA Holdings, LLC (the “Seller”) of all of the outstanding membership interests and stock in the Verde Companies. Total consideration was approximately $91.2 million , of which approximately $20.8 million was used to purchase positive net working capital, subject to adjustments. The Company funded the closing consideration of $85.8 million through: (i) approximately $6.8 million of cash on hand, (ii) approximately $15.0 million in subordinated debt from the Company's founder and majority shareholder through an existing subordinated debt facility, (iii) approximately $44.0 million in borrowings under its senior secured revolving credit facility, and (iv) the issuance by CenStar to the Seller of a promissory note in the aggregate principal amount of $20.0 million (the “Promissory Note”). In addition to the consideration paid at closing, CenStar is obligated to pay 100% of the Adjusted EBITDA earned by the Verde Companies for the 18 months following closing that exceeds certain thresholds, subject to the Verde Companies’ ability to achieve defined customer count criteria (the “Verde Earnout”). The Verde Earnout was valued at $5.4 million on the acquisition date. In determining the fair value of the Verde Earnout, the Company forecasted certain expected performance targets and calculated the probability of such forecast being attained. Upon the closing of the acquisition, the Verde Companies became restricted subsidiaries and co-borrowers under the Company’s Senior Credit Facility. The Verde Earnout was based on achievement by the Verde Companies of certain performance targets over the 18 month period following the closing of the acquisition of the Verde Companies. The Verde Earnout was valued at $5.4 million as of July 1, 2017, the acquisition date. The Company and the Seller agreed to terminate the Verde Earnout on January 12, 2018, and settled the obligation with the issuance of a $5.9 million promissory note payable to the Seller in June 2019 (the “Verde Earnout Termination Note”). The Company recorded a $0.3 million increase in fair value of the Verde Earnout in general and administrative expenses and classified the liability as long-term debt as of December 31, 2017 . During the year ended December 31, 2017 , the Company recorded accretion of $0.2 million to reflect the impact of the time value of the liability. See discussion of the Verde Earnout Termination Note in Note 8 "Debt." The acquisition of the Verde Companies was accounted for under the acquisition method in accordance with ASC 805, Business Combinations (“ASC 805”). The allocation of purchase consideration was based upon the estimated fair value of the tangible and identifiable intangible assets acquired and liabilities assumed in the acquisition. The allocation was made to major categories of assets and liabilities based on management’s best estimates, and supported by independent third-party analyses. The excess of the purchase price over the estimated fair value of tangible and intangible assets acquired and liabilities assumed was allocated to goodwill. The allocation of the purchase consideration is as follows (in thousands): December 31, 2017 Cash and restricted cash $ 1,653 Property and equipment 4,560 Intangible assets - customer relationships 28,700 Intangible assets - trademarks 3,000 Goodwill 39,207 Net working capital, net of cash acquired 19,132 Deferred tax liability (3,126 ) Fair value of derivative liabilities (1,942 ) Total $ 91,184 Finalization of the Company's actual working capital adjustment with the Seller is pending as of December 31, 2017. An estimated positive working capital adjustment between the Company and the Seller of approximately $0.5 million was recorded as of December 31, 2017 and is included in accounts receivable. Customer relationships The acquired customer relationships intangibles related to the Verde Companies are reflective of the Verde Companies' customer base, and were valued using an excess earnings method under the income approach. Using this method, the Company estimated the future cash flows resulting from the existing customer relationships, considering attrition as well as charges for contributory assets, such as net working capital, intangible assets, fixed assets, and assembled workforce. These future cash flows were then discounted using an appropriate risk-adjusted rate of return to arrive at the present value of the expected future cash flows. These customer relationships were bifurcated between unhedged and hedged and will be amortized to depreciation and amortization based on the expected future net cash flows by year and expensed to retail cost of revenues based on the expected term of the underlying fixed price contract acquired in each reporting period, respectively. Trademark The fair value of the Verde Companies' trademark is reflective of the value associated with the recognition and reputation of the Verde Companies to target markets. The fair value of the trademark was valued using a royalty savings method under the income approach. The value is based on the savings the Company would realize from owning the trademark rather than paying a royalty for the use of that trademark. Under this approach, the Company estimated the present value of the expected cash flows resulting from avoiding royalty payments to use a third party trademark. We analyzed market royalty rates charged for licensing trademarks and applied an expected royalty rate to a forecast of estimated revenue, which was then discounted using an appropriate risk adjusted rate of return. The trademark is being amortized over the estimated five -year life of the asset on a straight-line basis. Goodwill The excess of the purchase consideration over the estimated fair value of the amounts initially assigned to the identifiable assets acquired and liabilities assumed was recorded as goodwill. Goodwill arose on the acquisition of the Verde Companies primarily due the value of its assembled workforce, its proprietary sales channels, and access to new utility service territories. Goodwill recorded in connection with the acquisition of the Verde Companies is deductible for income tax purposes because the Verde Companies was an acquisition of all of the assets of the Verde Companies. The valuation and purchase price allocation of the Verde Companies was based on a preliminary fair value analysis. The Company anticipates adjustments to the working capital amounts that are expected to be finalized prior to the measurement period's expiration. The Verde Companies contributed revenues of $76.0 million and earnings of $1.2 million to the Company for the year ended December 31, 2017 . The following unaudited pro forma revenue and earnings summary presents consolidated information of the Company as if the acquisition had occurred on January 1, 2016 (in thousands): Year Ended December 31, 2017 2016 Revenues $ 868,415 $ 716,696 Earnings $ 18,047 $ 17,860 The pro forma results are not necessarily indicative of our consolidated results of operations in future periods or the results that actually would have been realized had the companies operated on a combined basis during the periods presented. The revenue and earnings for the twelve months ended December 31, 2017 reflects actual results of operations for the period from July 1, 2017 through December 31, 2017, the period the financial results were fully combined. The pro forma results include adjustments primarily related to amortization of acquired intangibles, and certain accounting policy alignments as well as direct and incremental acquisition related costs reflected in the historical financial statements. The preliminary purchase price allocation was used to prepare the pro forma adjustments. The final allocation could differ materially from the preliminary allocation used in the pro forma adjustments.

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Equity	4. Equity Non-controlling Interest The Company holds an economic interest and is the sole managing member in Spark HoldCo, with NuDevco Retail and Retailco holding the remaining economic interest in Spark HoldCo. As a result, the Company has consolidated the financial position and results of operations of Spark HoldCo and reflected the economic interest retained by NuDevco Retail and Retailco as a non-controlling interest. The Company and NuDevco Retail and Retailco owned the following economic interests in Spark HoldCo at December 31, 2016 and December 31, 2017 , respectively. Non-controlling Interest Economic Interest The Company NuDevco Retail and Retailco (1) (2) December 31, 2016 38.85 % 61.15 % December 31, 2017 38.12 % 61.88 % (1) In January 2016, Retailco succeeded to the interest of NuDevco Retail Holdings of its Class B common stock and an equal number of Spark HoldCo units it held pursuant to a series of transfers. (2) In January 2017, Retailco converted the CenStar Note and Oasis Note into 269,462 and 766,180 shares, respectively, of Class B common stock. The following table summarizes the portion of net income and income tax expense (benefit) attributable to non-controlling interest (in thousands): 2017 2016 2015 Net income allocated to non-controlling interest $ 56,696 $ 52,300 $ 21,779 Income tax expense (benefit) allocated to non-controlling interest (731 ) 1,071 (331 ) Net income attributable to non-controlling interest $ 57,427 $ 51,229 $ 22,110 Stock Split On May 22, 2017, the Company authorized and approved a two -for-one stock split of the Company's issued Class A common stock and Class B common stock, which was effected through a stock dividend (the "Stock Split"). Shareholders of record at the close of business on June 5, 2017 were issued one additional share of Class A common stock or Class B common stock of the Company for each share of Class A common stock or Class B common stock, respectively, held by such shareholder on that date. Such additional shares of Class A common stock or Class B common stock were distributed on June 16, 2017. All shares and per share amounts in this report have been retrospectively restated to reflect the Stock Split. Share Repurchase Program On May 24, 2017, the Company authorized a share repurchase program of up to $50.0 million of Spark Class A common stock through December 31, 2017. The Company funds the program through available cash balances, its credit facilities, and operating cash flows. The shares of Class A common stock may be repurchased from time to time in the open market or in privately negotiated transactions based on ongoing assessments of capital needs, the market price of the Class A common stock, and other factors, including general market conditions. The repurchase program does not obligate Spark to acquire any particular amount of Class A common stock and it may be modified or suspended at any time, and can be terminated prior to completion. The Company uses the cost method to account for its treasury shares. Purchases of shares of Class A common stock are recorded at cost, and the gross cost of the Class A common stock purchased is charged to a contra equity account entitled "Treasury Stock." During the year ended December 31, 2017 , the Company repurchased 99,446 shares of its Class A common stock at a weighted-average price of $20.22 per share, for a total cost of approximately $2.0 million . Class A Common Stock The Company had a total of 13,135,636 and 12,993,118 shares of its Class A common stock outstanding at December 31, 2017 and 2016 , respectively, and 99,446 and zero shares of treasury stock at December 31, 2017 and 2016 , respectively. Each share of Class A common stock holds economic rights and entitles its holder to one vote on all matters to be voted on by shareholders generally. All shares and per share amounts in this report have been retrospectively restated to reflect the Stock Split. Issuance of Class A Common Stock Upon Vesting of Restricted Stock Units For the year ended December 31, 2017 , 356,014 restricted stock units vested, with 241,965 shares of common stock distributed to the holders of these units and 114,049 shares of common stock withheld by the Company to cover taxes owed on the vesting of such units. For the year ended December 31, 2016 , 395,056 restricted stock units vested, with 305,872 shares of common stock distributed to the holders of these units and 89,184 shares of common stock withheld by the Company to cover taxes owed on the vesting of such units. Conversion of Class B Common Stock to Class A Common Stock On February 3, 2016, April 1, 2016 and June 8, 2016, Retailco exchanged 2,000,000 , 3,450,000 and 1,000,000 , respectively, of its Spark HoldCo units (together with a corresponding number of shares of Class B common stock) for shares of Class A common stock at an exchange ratio of one share of Class A common stock for each Spark HoldCo unit (and corresponding share of Class B common stock) exchanged. Refer to Note 12 "Income Taxes" for further discussion. Class B Common Stock The Company had a total of 21,485,126 and 20,449,484 shares of its Class B common stock outstanding at December 31, 2017 and 2016 , respectively. Each share of Class B common stock, all of which are held by NuDevco Retail and Retailco, have no economic rights but entitles its holder to one vote on all matters to be voted on by shareholders generally. All outstanding shares and per share amounts in this report have been retrospectively restated to reflect the Stock Split. Holders of Class A common stock and Class B common stock vote together as a single class on all matters presented to our shareholders for their vote or approval, except as otherwise required by applicable law or by our certificate of incorporation. Issuance of Class B Common Stock On August 1, 2016, the Company issued 1,399,484 shares of Class B common stock to Retailco in connection with the acquisition of the Provider Companies. On August 23, 2016, the Company issued 4,000,000 shares of Class B common stock to Retailco in connection with the acquisition of Major Energy Companies. Preferred Stock The Company has 20,000,000 shares of authorized preferred stock for which there are 1,704,339 and zero issued and outstanding shares at December 31, 2017 and 2016 . Conversion of CenStar and Oasis Notes On October 5, 2016, RAC issued to the Company an irrevocable commitment to convert the CenStar Note and Oasis Note into 269,462 and 766,180 shares, respectively, of Class B common stock (and related Spark HoldCo units) on January 8, 2017 and January 31, 2017, respectively. Refer to Note 8 "Debt" for further discussion. On January 8, 2017 and January 31, 2017, respectively, the CenStar Note and Oasis Note were converted into 269,462 and 766,180 shares of Class B common stock (and related Spark HoldCo units). Refer to Note 8 "Debt" for further discussion. Earnings Per Share Basic earnings per share (“EPS”) is computed by dividing net income attributable to stockholders (the numerator) by the weighted-average number of Class A common shares outstanding for the period (the denominator). Class B common shares are not included in the calculation of basic earnings per share because they are not participating securities and have no economic interest in the Company. Diluted earnings per share is similarly calculated except that the denominator is increased (1) using the treasury stock method to determine the potential dilutive effect of the Company's outstanding unvested restricted stock units, (2) using the if-converted method to determine the potential dilutive effect of the Company's Class B common stock and (3) using the if-converted method to determine the potential dilutive effect of the outstanding convertible subordinated notes into the Company's Class B common stock. All shares and per share amounts in this report have been retrospectively restated to reflect the Stock Split. The following table presents the computation of earnings per share for the years ended December 31, 2017 and 2016 (in thousands, except per share data): Year Ended December 31, 2017 2016 2015 Net income attributable to Spark Energy, Inc. stockholders $ 18,854 $ 14,444 $ 3,865 Less: Dividend on Series A preferred stock 3,038 — — Net income attributable to stockholders of Class A common stock $ 15,816 $ 14,444 $ 3,865 Basic weighted average Class A common shares outstanding 13,143 11,402 6,129 Basic EPS attributable to stockholders $ 1.20 $ 1.27 $ 0.63 Net income attributable to stockholders of Class A common stock $ 15,816 $ 14,444 $ 3,865 Effect of conversion of Class B common stock to shares of Class A common stock — — — Effect of conversion of convertible subordinated notes into shares of Class B common stock and shares of Class B common stock into shares of Class A common stock (1) — (310 ) (334 ) Diluted net income attributable to stockholders of Class A common stock $ 15,816 $ 14,134 $ 3,531 Basic weighted average Class A common shares outstanding 13,143 11,402 6,129 Effect of dilutive Class B common stock — — — Effect of dilutive convertible subordinated notes into shares of Class B common stock and shares of Class B common stock into shares of Class A common stock — 1,010 420 Effect of dilutive restricted stock units 203 278 106 Diluted weighted average shares outstanding 13,346 12,690 6,655 Diluted EPS attributable to stockholders $ 1.19 $ 1.11 $ 0.53 (1) The CenStar Note and Oasis Note converted into 269,462 and 766,180 shares of Class B common stock on January 8, 2017, and January 31, 2017, respectively. The conversion of shares of Class B common stock to shares of Class A common stock was not recognized in dilutive earnings per share for the years ended December 31, 2017 as the effect of the conversion was antidilutive. Variable Interest Entity On January 1, 2016, we adopted ASU No. 2015-02, Consolidation (Topic 810) (“ASU 2015-02”) . ASU 2015-02 changed the analysis that a reporting entity must perform to determine whether it should consolidate certain types of legal entities. Upon adoption, we continued to consolidate Spark HoldCo, but considered Spark HoldCo to be a variable interest entity requiring additional disclosures in the footnotes of our consolidated financial statements. Spark HoldCo is a variable interest entity due to its lack of rights to participate in significant financial and operating decisions and inability to dissolve or otherwise remove its management. Spark HoldCo owns all of the outstanding membership interests in each of the operating subsidiaries through which the Company operates. The Company is the sole managing member of Spark HoldCo, manages Spark HoldCo's operating subsidiaries through this managing membership interest, and is considered the primary beneficiary of Spark HoldCo. The assets of Spark HoldCo cannot be used to settle the obligations of the Company except through distributions to the Company, and the liabilities of Spark HoldCo cannot be settled by the Company except through contributions to Spark HoldCo. The following table includes the carrying amounts and classification of the assets and liabilities of Spark HoldCo that are included in the Company's consolidated balance sheet as of December 31, 2017 (in thousands): December 31, 2017 Assets Current assets: Cash and cash equivalents $ 29,385 Accounts receivable 158,814 Other current assets 105,165 Total current assets 293,364 Non-current assets: Goodwill 120,154 Other assets 62,552 Total non-current assets 182,706 Total Assets $ 476,070 Liabilities Current liabilities: Accounts Payable and Accrued Liabilities $ 110,152 Current portion of Senior Credit Facility 7,500 Contingent consideration 4,024 Other current liabilities 8,933 Total current liabilities 130,609 Long-term liabilities: Long-term portion of Senior Credit Facility 117,750 Contingent consideration 626 Other long-term liabilities 663 Total long-term liabilities 119,039 Total Liabilities $ 249,648

Preferred Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Preferred Stock	5. Preferred Stock On March 15, 2017, the Company issued 1,610,000 shares of 8.75% Series A Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Stock ("Series A Preferred Stock"), par value $0.01 per share and liquidation preference $25.00 per share, plus accumulated and unpaid dividends, at a price to the public of $25.00 per share ( $24.21 per share to the Company, net of underwriting discounts and commissions). The Company received approximately $39.0 million in net proceeds from the offering, after deducting underwriting discounts and commissions and a structuring fee. Offering expenses of $1.0 million were recorded as a reduction to the carrying value of the Series A Preferred Stock. The net proceeds from the offering were contributed to Spark HoldCo to use for general corporate purposes. On July 21, 2017, the Company entered into an At-the-Market Issuance Sales Agreement ("the ATM Agreement") with FBR Capital Markets & Co. as sales agent (the "Agent"). Pursuant to the terms of the ATM Agreement, the Company may sell from time to time through the Agent the Company's Series A Preferred Stock, having an aggregate offering price of up to $50.0 million . During the year ended December 31, 2017 , the Company sold an aggregate of 94,339 shares of Series A Preferred Stock under the ATM Agreement. The Company received net proceeds of $2.4 million and paid compensation to the sales agent of less than $0.1 million with respect to these sales. Holders of the Series A Preferred Stock have no voting rights, except in specific circumstances of delisting or in the case the dividends are in arrears as specified in the Series A Preferred Stock Certificate of Designations. From March 15, 2017, the Series A Preferred Stock issuance date, to, but not including, April 15, 2022, the Series A Preferred Stock will accrue dividends at an annual percentage rate of three-month LIBOR plus 6.578% . The liquidation preference provisions of the Series A Preferred Stock were considered contingent redemption provisions because there were certain rights granted to the holders of the Series A Preferred Stock that were not solely within the control of the Company upon a change in control of the Company. Accordingly, the Series A Preferred Stock is presented within the mezzanine portion of the accompanying consolidated balance sheet. The Company had a total of 1,704,339 shares of Series A Preferred Stock issued and outstanding at December 31, 2017 and no shares of Series A Preferred Stock issued and outstanding at December 31, 2016 . During the year ended December 31, 2017 , the Company paid $2.1 million in dividends to holders of the Series A Preferred Stock. As of December 31, 2017 , the Company had accrued $0.9 million related to dividends to holders of the Series A Preferred Stock. This dividend was paid on January 15, 2018 . A summary of the Company's mezzanine equity for the year ended December 31, 2017 is as follows: (in thousands) Mezzanine equity at December 31, 2016 $ — Issuance of Series A Preferred Stock, net of issuance cost 40,241 Accumulated dividends on Series A Preferred Stock 932 Mezzanine equity at December 31, 2017 $ 41,173 In connection with the issuance of the Series A Preferred Stock, the Company and Spark HoldCo entered into the Third Amended and Restated Spark HoldCo Limited Liability Company Agreement to amend the prior agreement to provide for, among other things, the designation and issuance of Spark HoldCo Series A preferred units, as another equity security of Spark HoldCo to be issued concurrently with the issuance of Series A Preferred Stock by the Company, including specific terms relating to distributions by Spark HoldCo in connection with the payment by the Company of dividends on the Series A Preferred Stock, the priority of liquidating distributions by Spark HoldCo, the allocation of income and loss to the Company in connection with distributions by Spark HoldCo on Series A preferred units, and other terms relating to the redemption and conversion by the Company of the Series A Preferred Stock. Public Offering of Series A Preferred Stock On January 23, 2018, the Company commenced a public offering of its 8.75% Series A Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Stock (“Series A Preferred Stock”) pursuant to an effective shelf registration statement on Form S-3 previously filed with the SEC. At the time of issuance, Spark granted the underwriters a 30 -day option to purchase additional shares of Series A Preferred Stock. The offering closed on January 26, 2018. As of the filing date, the Company sold an aggregate of 2,000,000 shares of Series A Preferred Stock. The Company received net proceeds from the offering of approximately $48.9 million (net of underwriting discounts, commissions and a structuring fee).

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	6. Property and Equipment Property and equipment consist of the following amounts as of (in thousands): Estimated December 31, 2017 December 31, 2016 Information technology 2 – 5 $ 34,103 $ 29,675 Leasehold improvements 2 – 5 4,568 4,568 Furniture and fixtures 2 – 5 1,964 1,024 Building improvements 2 – 5 809 — Total 41,444 35,267 Accumulated depreciation (33,169 ) (30,561 ) Property and equipment—net $ 8,275 $ 4,706 Information technology assets include software and consultant time used in the application, development and implementation of various systems including customer billing and resource management systems. As of December 31, 2017 and 2016 , information technology includes $1.2 million and $1.1 million , respectively, of costs associated with assets not yet placed into service. Depreciation expense recorded in the consolidated statements of operations was $2.6 million , $2.1 million and $1.6 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Goodwill, Customer Relationship

Goodwill, Customer Relationships and Trademarks	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, Customer Relationships and Trademarks	5 years 3,601 Total $ 62,050" id="sjs-B4">7. Goodwill, Customer Relationships and Trademarks Goodwill, customer relationships and trademarks consist of the following amounts as of (in thousands): December 31, 2017 December 31, 2016 Goodwill $ 120,154 $ 79,147 Customer Relationships — Acquired (1) Cost $ 93,371 $ 63,571 Accumulated amortization (46,681 ) (31,660 ) Customer Relationships —Acquired, net $ 46,690 $ 31,911 Customer Relationships — Other (2) Cost $ 12,336 $ 4,320 Accumulated amortization (5,534 ) (2,708 ) Customer Relationships —Other, net $ 6,802 $ 1,612 Trademarks (3) Cost $ 9,770 $ 6,770 Accumulated amortization (1,212 ) (431 ) Trademarks, net $ 8,558 $ 6,339 (1) Customer relationships—Acquired represent those customer acquisitions accounted for under the acquisition method in accordance with ASC 805. See Note 3 "Acquisitions" for further discussion. (2) Customer relationships—Other represent portfolios of customer contracts not accounted for in accordance with ASC 805 as these acquisitions were not in conjunction with the acquisition of businesses. See Note 16 "Customer Acquisitions" for further discussion. (3) Trademarks reflect values associated with the recognition and positive reputation of acquired businesses accounted for as part of the acquisition method in accordance with ASC 805 through the acquisitions of CenStar, Oasis, the Provider Companies, the Major Energy Companies and the Verde Companies. These trademarks are recorded as other assets in the consolidated balance sheets. See Note 3 "Acquisitions" for further discussion. Changes in goodwill, customer relationships and trademarks consisted of the following (in thousands): Goodwill (1) Customer Relationships— Acquired & Non-Compete Agreements Customer Relationships — Other Trademarks Balance at December 31, 2014 $ — $ — $ 1,501 $ — Additions $ — $ — $ 2,731 $ — Acquisition of CenStar 6,396 5,494 — 651 Acquisition of Oasis 11,983 9,389 — 617 Amortization expense — (4,503 ) (1,183 ) (74 ) Balance at December 31, 2015 $ 18,379 $ 10,380 $ 3,049 $ 1,194 Additions $ — $ — $ — $ — Acquisition of Provider Companies 26,040 24,417 — 529 Acquisition of Major Energy Companies 34,728 24,271 — 4,973 Amortization expense — (27,157 ) (1,437 ) (357 ) Balance at December 31, 2016 $ 79,147 $ 31,911 $ 1,612 $ 6,339 Additions (Major Working Capital Adjustment) $ 260 $ — $ — $ — Acquisition of Perigee 1,540 1,100 — — Acquisition of Verde 39,207 28,700 — 3,000 Additions (Other) (2) — — 8,016 — Amortization expense — (15,021 ) (2,826 ) (781 ) Balance at December 31, 2017 $ 120,154 $ 46,690 $ 6,802 $ 8,558 (1) Changes in goodwill for the year ended December 31, 2017 include NG&E's working capital settlement with the Major Energy Companies' sellers of $0.3 million , Perigee's goodwill of $1.5 million , and the Verde Companies' goodwill of $39.2 million . (2) Includes $8.0 million related to customer contract purchases for the year ended December 31, 2017 . The acquired customer relationship intangibles related to Major Energy Companies, the Provider Companies, and the Verde Companies were bifurcated between hedged and unhedged customer contracts. The unhedged customer contracts are amortized to depreciation and amortization based on the expected future cash flows by year. The hedged customer contracts were evaluated for favorable or unfavorable positions at the time of acquisition and amortized to retail cost of revenue based on the expected term and position of the underlying fixed price contract in each reporting period. For the years ended December 31, 2017 , 2016 , and 2015 , respectively, approximately $0.3 million , $15.8 million , and zero of the $15.0 million , $27.2 million , and $4.5 million customer relationship amortization expense is included in the cost of revenues. Estimated future amortization expense for customer relationships and trademarks at December 31, 2017 is as follows (in thousands): Year Ending December 31, 2018 $ 19,469 2019 14,894 2020 10,474 2021 8,912 2022 4,700 > 5 years 3,601 Total $ 62,050

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	8. Debt Balance Sheet and Income Statement Summary Debt consists of the following amounts as of (in thousands): December 31, 2017 December 31, 2016 Current portion of Senior Credit Facility—Bridge Loan (5) $ 7,500 $ — Current portion of Prior Senior Credit Facility—Working Capital Line (1) — 29,000 Current portion of Prior Senior Credit Facility—Acquisition Line (2) — 22,287 Current portion of Note Payable—Pacific Summit Energy — 15,501 Convertible subordinated notes to affiliate (3) — 6,582 Current portion of Note Payable—Verde 13,443 — Total current debt 20,943 73,370 Long-term portion of Senior Credit Facility (4) (5) 117,750 — Subordinated Debt — 5,000 Long-term portion of Note Payable—Verde 7,051 — Total long-term debt 124,801 5,000 Total debt $ 145,744 $ 78,370 (1) As of December 31, 2016 , the Company had $29.6 million in letters of credit issued. (2) As of December 31, 2016 , the weighted average interest rate on the current portion of our Prior Senior Credit Facility was 4.93% . (3) On October 5, 2016, RAC issued to the Company an irrevocable commitment to convert the CenStar Note and the Oasis Note into shares of Class B common stock on January 8, 2017 and January 31, 2017, respectively. RAC assigned the CenStar Note and Oasis Note to Retailco on January 4, 2017, and on January 8, 2017 and January 31, 2017, the CenStar Note and Oasis Note were converted into 269,462 and 766,180 shares of Class B common stock, respectively. (4) As of December 31, 2017 , the Company had $47.2 million in letters of credit issued. (5) As of December 31, 2017 , the weighted average interest rate on our Senior Credit Facility was 4.61% . Deferred financing costs were $1.6 million and $0.4 million as of December 31, 2017 and 2016 , respectively. Of these amounts, $1.2 million and $0.4 million is recorded in other current assets in the consolidated balance sheets as of December 31, 2017 and 2016 , respectively, and $0.4 million and zero is recorded in other assets in the consolidated balance sheets as of December 31, 2017 and 2016 , respectively, representing capitalized financing costs related to our Senior Credit Facility and Prior Senior Credit Facility. Interest expense consists of the following components for the periods indicated (in thousands): Years Ended December 31, 2017 2016 2015 Interest incurred on Senior Credit Facility $ 3,275 $ 1,730 $ 1,144 Accretion related to Earnouts (1) 4,108 5,060 — Letters of credit fees and commitment fees 1,125 883 517 Amortization of deferred financing costs (2) 1,035 668 412 Interest incurred on convertible subordinated notes to affiliate (3) 1,052 518 207 Interest incurred on subordinated debt 167 — — Interest on Verde promissory note 372 — — Interest expense $ 11,134 $ 8,859 $ 2,280 (1) Includes accretion related to the Provider Earnout of $0.1 million , the Major Earnout of $3.8 million , and the Verde Earnout of $0.2 million for the year ended December 31, 2017 and accretion related to the Provider Earnout of $0.1 million and the Major Earnout of $4.9 million for the year ended December 31, 2016 . (2) Write offs of deferred financing costs included in the above amortization were $0.1 million in connection with the amended and restated Prior Senior Credit Facility on July 8, 2015, $0.3 million upon extinguishment of the Seventh Amended Credit Facility and $0.1 million in connection with the execution of the Seventh Amended Credit Facility for the year ended December 31, 2015 . (3) Includes amortization of the discount on the convertible subordinated notes to affiliates of zero , $0.2 million , and less than $0.1 million for the years ended December 31, 2017 , 2016 , and 2015 . Prior Senior Credit Facility The Company, as guarantor, and Spark HoldCo (the “Borrower,” and together with Spark Energy, LLC, Spark Energy Gas, LLC, CenStar Energy Corp, CenStar Operating Company, LLC, Oasis, Oasis Power, LLC, Electricity Maine, LLC, Electricity N.H., LLC, and Provider Power Mass, LLC, each a subsidiary of Spark HoldCo, the “Co-Borrowers”) were party to a senior secured revolving credit facility (“Prior Senior Credit Facility”), which included a senior secured revolving working capital facility up to $82.5 million ("Working Capital Line") and a secured revolving line of credit of $25.0 million ("Acquisition Line") to be used specifically for the financing of up to 75% of the cost of acquisitions with the remainder to be financed by the Company either through cash on hand or the issuance of subordinated debt or equity. The Prior Senior Credit Facility was secured by pledges of the equity of the portion of Spark HoldCo owned by the Company and of the equity of Spark HoldCo’s subsidiaries (excluding the Major Energy Companies) and the Co-Borrowers’ present and future subsidiaries, all of the Co-Borrowers’ and their subsidiaries’ present and future property and assets, including accounts receivable, inventory and liquid investments, and control agreements relating to bank accounts. The Major Energy Companies were excluded from the definition of "Borrowers" under the Prior Senior Credit Facility. Accordingly, we did not factor in their working capital into our working capital covenants. The Prior Senior Credit Facility had a maturity date of July 8, 2017. The outstanding balances under the Working Capital Line and the Acquisition Line were paid in full on May 19, 2017 upon execution of the Company's new Senior Credit Facility. Senior Credit Facility On May 19, 2017 (the “Closing Date”), the Company, as guarantor, and Spark HoldCo (the “Borrower” and, together with SE, SEG, CenStar, CenStar Operating Company, LLC, Oasis, Oasis Power, LLC, the Provider Companies, the Major Energy Companies and Perigee Energy, LLC, each subsidiaries of Spark HoldCo, the “Co-Borrowers”), entered into a senior secured borrowing base credit facility (the “Senior Credit Facility”) in an aggregate amount of $120.0 million . The Verde Companies became Co-Borrowers upon the completion of our acquisition of the Verde Companies. On November 2, 2017, the Company and Co-Borrowers entered into an amendment to the Senior Credit Facility, which entitles the co-borrowers to elect to increase total commitments under the Senior Credit Facility to $200.0 million . In connection with any such increase in commitments, the various limits on advances for Working Capital Loans, Letters of Credit and Bridge Loans increased accordingly. On November 30, 2017, we exercised the accordion feature in the Senior Credit Facility, expanding commitments to an aggregate amount of $185.0 million . As of December 31, 2017, there was $125.3 million outstanding under the Senior Credit Facility, and there was approximately $12.5 million available borrowing capacity (which includes a $47.2 million reduction for outstanding letters of credit). The Senior Credit Facility will mature on May 19, 2019, and all amounts outstanding thereunder will be payable on the maturity date. Borrowings under the Bridge Loan sublimit will be repaid 25% per year on a quarterly basis (or 6.25% per quarter), with the remainder due at maturity. On January 11, 2018 and January 23, 2018, we exercised the accordion feature in the Senior Credit Facility for an additional $10.0 million and $5.0 million , respectively, in commitments by existing lenders. These exercises of the accordion feature of the Senior Credit Facility brought total commitments under the Senior Credit Facility to $200.0 million . Subject to applicable sublimits and terms of the Senior Credit Facility, borrowings are available for the issuance of letters of credit (“Letters of Credit”), working capital and general purpose revolving credit loans up to $200.0 million (“Working Capital Loans”), and bridge loans up to $50.0 million (“Bridge Loans”) for the purpose of partial funding for acquisitions. Borrowings under the Senior Credit Facility may be used to refinance loans outstanding under the previous Senior Credit Facility, pay fees and expenses in connection with the current Senior Credit Facility, finance ongoing working capital requirements and general corporate purpose requirements of the Co-Borrowers, to provide partial funding for acquisitions, as allowed under terms of the Senior Credit Facility, and to make open market purchases of the Company’s Class A common stock. At our election, the interest rate for Working Capital Loans and Letters of Credit under the Senior Credit Facility is generally determined by reference to: • the Eurodollar rate plus an applicable margin of up to 3.00% per annum (based on the prevailing utilization); or • the alternate base rate plus an applicable margin of up to 2.00% per annum (based on the prevailing utilization). The alternate base rate is equal to the highest of (i) the prime rate (as published in the Wall Street Journal), (ii) the federal funds rate plus 0.50% per annum, or (iii) the reference Eurodollar rate plus 1.00% . Bridge Loan borrowings, if any, under the Senior Credit Facility are generally determined by reference to: • the Eurodollar rate plus an applicable margin of 3.75% per annum; or • the alternate base rate plus an applicable margin of 2.75% per annum. The alternate base rate is equal to the highest of (i) the prime rate (as published in the Wall Street Journal), (ii) the federal funds rate plus 0.50% per annum, or (iii) the reference Eurodollar rate plus 1.00% . The Co-Borrowers will pay a commitment fee of 0.50% quarterly in arrears on the unused portion of the Senior Credit Facility. In addition, the Co-Borrowers will be subject to additional fees including an upfront fee, an annual agency fee, and letter of credit fees based on a percentage of the face amount of letters of credit payable to any syndicate member that issues a letter of credit. The Senior Credit Facility contains covenants that, among other things, require the maintenance of specified ratios or conditions as follows: • Minimum Fixed Charge Coverage Ratio . Spark Energy, Inc. must maintain a minimum fixed charge coverage ratio of not less than 1.25 to 1.00. The Fixed Charge Coverage Ratio is defined as the ratio of (a) Adjusted EBITDA to (b) the sum of consolidated (with respect to the Company and the Co-Borrowers) interest expense (other than interest paid-in-kind in respect of any Subordinated Debt but including interest in respect of that certain promissory note made by Censtar Energy Corp in connection with the permitted acquisition from Verde Energy USA Holdings, LLC), letter of credit fees, commitment fees, acquisition earn-out payments (excluding earnout payments funded with proceeds from newly issued preferred or common equity of the Company), distributions, the aggregate amount of repurchases of the Company’s Class A common stock or commitments for such purchases, taxes and scheduled amortization payments. • Maximum Total Leverage Ratio . Spark Energy, Inc. must maintain a ratio of total indebtedness (excluding eligible subordinated debt) to Adjusted EBITDA of no more than 2.00 to 1.00. The Senior Credit Facility contains various negative covenants that limit the Company’s ability to, among other things, do any of the following: • incur certain additional indebtedness; • grant certain liens; • engage in certain asset dispositions; • merge or consolidate; • make certain payments, distributions, investments, acquisitions or loans; • materially modify certain agreements; or • enter into transactions with affiliates The Senior Credit Facility is secured by pledges of the equity of the portion of Spark HoldCo owned by the Company, the equity of Spark HoldCo’s subsidiaries, the Co-Borrowers’ present and future subsidiaries, and substantially all of the Co-Borrowers’ and their subsidiaries’ present and future property and assets, including accounts receivable, inventory and liquid investments, and control agreements relating to bank accounts. Spark Energy, Inc. is entitled to pay cash dividends to the holders of the Series A Preferred Stock and Class A common stock and will be entitled to repurchase up to an aggregate amount of 10,000,000 shares of the Company’s Class A common stock through one or more normal course open market purchases through NASDAQ so long as: (a) no default exists or would result therefrom; (b) the Co-Borrowers are in pro forma compliance with all financial covenants before and after giving effect thereto; and (c) the outstanding amount of all loans and letters of credit does not exceed the borrowing base limits. The Senior Credit Facility contains certain customary representations and warranties and events of default. Events of default include, among other things, payment defaults, breaches of representations and warranties, covenant defaults, cross-defaults and cross-acceleration to certain indebtedness, certain events of bankruptcy, certain events under ERISA, material judgments in excess of $5.0 million , certain events with respect to material contracts, actual or asserted failure of any guaranty or security document supporting the Senior Credit Facility to be in full force and effect, failure of Nathan Kroeker to retain his position as President and Chief Executive Officer of the Company, and failure of W. Keith Maxwell III to retain his position as chairman of the board of directors. A default will also occur if at any time W. Keith Maxwell III ceases to, directly or indirectly, own at least 13,600,000 Class A and Class B shares on a combined basis (to be adjusted for any stock split, subdivisions or other stock reclassification or recapitalization), and a controlling percentage of the voting equity interest of the Company, and certain other changes in control. If such an event of default occurs, the lenders under the Senior Credit Facility would be entitled to take various actions, including the acceleration of amounts due under the facility and all actions permitted to be taken by a secured creditor. In addition, the Senior Credit Facility contains affirmative covenants that are customary for credit facilities of this type. The covenants include delivery of financial statements, including any filings made with the SEC, maintenance of property and insurance, payment of taxes and obligations, material compliance with laws, inspection of property, books and records and audits, use of proceeds, payments to bank blocked accounts, notice of defaults and certain other customary matters. Convertible Subordinated Notes to Affiliate In connection with the financing of the CenStar acquisition, the Company, together with Spark HoldCo, issued the CenStar Note to RAC for $2.1 million on July 8, 2015 at an annual interest rate of 5% , payable semiannually. On October 5, 2016, RAC issued to the Company an irrevocable commitment to convert the CenStar Note into 269,462 shares of Class B common stock. RAC assigned the CenStar Note to Retailco on January 4, 2017, and on January 8, 2017, the CenStar Note was converted into 269,462 shares of Class B common stock. In connection with the financing of the Oasis acquisition, the Company, together with Spark HoldCo, issued the Oasis Note to RAC for $5.0 million on July 31, 2015 at an annual rate of 5% , payable semiannually. On October 5, 2016, RAC issued to the Company an irrevocable commitment to convert the Oasis Note into 766,180 shares of Class B common stock. RAC assigned the Oasis Note to Retailco on January 4, 2017, and on January 31, 2017 the Oasis Note was converted into 766,180 shares of Class B common stock. The conversion rate of $7.00 per share for the Oasis Note was fixed as of the date of the execution of the Oasis acquisition agreement on May 12, 2015. Due to a rise in the price of our common stock from May 12, 2015 to the closing of Oasis acquisition on July 31, 2015, the conversion rate of $7.00 per share was below the market price per share of Class A common stock of $8.11 on the issuance date of the Oasis Note on July 31, 2015. As a result, the Company assessed the Oasis Note for a beneficial conversion feature. Due to this conversion feature being "in-the-money" upon issuance, we recognized a beneficial conversion feature based on its intrinsic value of $0.8 million as a discount to the Oasis Note and as additional paid-in capital. This discount was amortized as interest expense under the effective interest method over the life of the Oasis Note through the conversion on January 31, 2017, at which time the remaining $1.0 million beneficial conversion feature was written-off and recognized as interest expense. Subordinated Debt Facility On December 27, 2016, we and Spark HoldCo jointly issued to Retailco, an entity owned by our Founder, a 5% subordinated note in the principal amount of up to $25.0 million . The subordinated note allows the Company and Spark HoldCo to draw advances in increments of no less than $1.0 million per advance up to the maximum principal amount of the subordinated note. The subordinated note matures in July 2020, and advances thereunder accrue interest at 5% per annum from the date of the advance. The Company has the right to capitalize interest payments under the subordinated note. The subordinated note is subordinated in certain respects to the Company's Senior Credit Facility pursuant to a subordination agreement. The Company may pay interest and prepay principal on the subordinated note so long as it is in compliance with its covenants under the Senior Credit Facility, is not in default under the Senior Credit Facility and has minimum availability of $5.0 million under the borrowing base under the Senior Credit Facility. Payment of principal and interest under the subordinated note is accelerated upon the occurrence of certain change of control or sale transactions. As of December 31, 2017 and 2016 , there were zero and $5.0 million , respectively, in outstanding borrowings under the subordinated note. Pacific Summit Energy LLC Prior to March 31, 2017, the Major Energy Companies were party to three trade credit arrangements with Pacific Summit Energy LLC (“Pacific Summit”), which consisted of purchase agreements, operating agreements relating to purchasing terms, security agreements, lockbox agreements and guarantees, and provided for the exclusive supply of gas and electricity on credit by Pacific Summit to the Major Energy Companies for resale to end users. Under these arrangements, when the costs that Pacific Summit paid to procure and deliver the gas and electricity exceeded the payments that the Major Energy Companies made attributable to the gas and electricity purchased, the Major Energy Companies incurred interest on the difference. The operating agreements also allowed Pacific Summit to provide credit support. Each form of borrowing incurred interest at the floating 90-day LIBOR rate plus 300 basis points (except for certain credit support guaranties that did not bear interest). In connection with these arrangements, the Major Companies granted first liens to Pacific Summit on a substantial portion of the Major Companies’ assets, including present and future accounts receivable, inventory, liquid assets, and control agreements relating to bank accounts. As of December 31, 2016 , the Company had aggregate outstanding amounts payable under these arrangements of approximately $15.5 million bearing an interest rate of approximately 4.0% . The Company was also the beneficiary under various credit support guarantees issued by Pacific Summit under these arrangements as of such date. On September 27, 2016, we notified Pacific Summit of our election to trigger the expiration of these arrangements. On March 31, 2017, the agreements were terminated. Verde Companies Promissory Note In connection with the financing of the Verde Companies acquisition, on July 1, 2017, CenStar issued a promissory note in the aggregate principal amount of $20.0 million (the "Verde Promissory Note") for a portion of the purchase price. The Verde Promissory Note required 18 monthly installments beginning on August 1, 2017, and accrued interest at 5% per annum from the date of issuance. The Verde Promissory Note, including principal and interest, was unsecured, but is guaranteed by the Company. Payment of principal and interest under the Verde Promissory Note was accelerated upon the occurrence of certain events of default. As of December 31, 2017 , there was $14.6 million outstanding under the Verde Promissory Note, of which $13.4 million is due in 2018. On January 12, 2018, CenStar issued to the Seller an amended and restated promissory note (the “Amended and Restated Verde Promissory Note”), which amended and restated the Verde Promissory Note in connection with the termination of our earnout obligations under the purchase agreement for the Verde Companies. The Amended and Restated Verde Promissory Note, effective January 12, 2018, retains the same maturity date as the Verde Promissory Note. The Amended and Restated Verde Promissory Note bears interest at a rate of 9% per annum beginning January 1, 2018. Principal and interest remain payable monthly on the first day of each month in which the Amended and Restated Verde Promissory Note is outstanding. CenStar will continue to deposit a portion of each payment under the Amended and Restated Verde Promissory Note into an escrow account, which serves as security for certain indemnification claims and obligations under the purchase agreement. The amount deposited into the escrow account has been increased from the Verde Promissory Note. All principal and interest payable under the Amended and Restated Verde Promissory Note remains subject to acceleration upon the occurrence of certain events of default, including the failure to pay any principal or interest when due under the Amended and Restated Verde Promissory Note. Verde Earnout Termination Note On January 12, 2018, we entered into an Agreement to Terminate Earnout Payments (the “Earnout Termination Agreement”) that terminates our obligation to make any required earnout payments under the purchase agreement for our acquisition of the Verde Companies in exchange for CenStar’s issuance to the Seller of a promissory note in the principal amount of $5.9 million (the “Verde Earnout Termination Note”). The Verde Earnout Termination Note, effective January 12, 2018, matures on June 30, 2019 (subject to early maturity upon certain events) and bears interest at a rate of 9% per annum. CenStar is permitted to withhold amounts otherwise due at maturity related to certain indemnifiable matters under the purchase agreement for our acquisition of the Verde Companies. Interest is payable monthly on the first day of each month in which the Verde Earnout Termination Note is outstanding, beginning on its issuance date. The principal and any outstanding interest is due on June 30, 2019. All principal and interest payable under the Verde Earnout Termination Note is accelerated upon the occurrence of certain events of default, including the failure to pay any principal or interest when due under the Verde Earnout Termination Note. The Company recorded the Verde Earnout Termination Note of $5.9 million as long-term debt as of December 31, 2017 .

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	9. Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (exit price) in an orderly transaction between market participants at the measurement date. Fair values are based on assumptions that market participants would use when pricing an asset or liability, including assumptions about risk and the risks inherent in valuation techniques and the inputs to valuations. This includes not only the credit standing of counterparties involved and the impact of credit enhancements but also the impact of the Company’s own nonperformance risk on its liabilities. The Company applies fair value measurements to its commodity derivative instruments and a contingent payment arrangement based on the following fair value hierarchy, which prioritizes the inputs to valuation techniques used to measure fair value into three broad levels: • Level 1—Quoted prices in active markets for identical assets and liabilities. Instruments categorized in Level 1 primarily consist of financial instruments such as exchange-traded derivative instruments. • Level 2—Inputs other than quoted prices recorded in Level 1 that are either directly or indirectly observable for the asset or liability, including quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in inactive markets, inputs other than quoted prices that are observable for the asset or liability, and inputs that are derived from observable market data by correlation or other means. Instruments categorized in Level 2 primarily include non-exchange traded derivatives such as over-the-counter commodity forwards and swaps and options. • Level 3—Unobservable inputs for the asset or liability, including situations where there is little, if any, observable market activity for the asset or liability. The Level 3 category includes estimated earnout obligations related to the Company's acquisitions. As the fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3), the Company maximizes the use of observable inputs and minimizes the use of unobservable inputs when measuring fair value. In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. In these cases, the lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Other Financial Instruments The carrying amount of cash and cash equivalents, accounts receivable, accounts receivable—affiliates, accounts payable, accounts payable—affiliates, and accrued liabilities recorded in the consolidated balance sheets approximate fair value due to the short-term nature of these items. The carrying amounts of the Senior Credit Facility and Prior Senior Credit Facility recorded in the consolidated balance sheets approximate fair value because of the variable rate nature of the Company’s line of credit. The fair value of our convertible subordinated notes to affiliates is not determinable for accounting purposes due to the affiliate nature and terms of the associated debt instrument with the affiliate. The fair value of the payable pursuant to tax receivable agreement—affiliate is not determinable for accounting purposes due to the affiliate nature and terms of the associated agreement with the affiliate. Assets and Liabilities Measured at Fair Value on a Recurring Basis The following tables present assets and liabilities measured and recorded at fair value in the Company’s consolidated balance sheets on a recurring basis by and their level within the fair value hierarchy as of (in thousands): Level 1 Level 2 Level 3 Total December 31, 2017 Non-trading commodity derivative assets $ 158 $ 33,886 $ — $ 34,044 Trading commodity derivative assets — 456 — 456 Total commodity derivative assets $ 158 $ 34,342 $ — $ 34,500 Non-trading commodity derivative liabilities $ (387 ) $ (950 ) $ — $ (1,337 ) Trading commodity derivative liabilities (555 ) (237 ) — (792 ) Total commodity derivative liabilities $ (942 ) $ (1,187 ) $ — $ (2,129 ) Contingent payment arrangement $ — $ — $ (4,650 ) $ (4,650 ) Level 1 Level 2 Level 3 Total December 31, 2016 Non-trading commodity derivative assets $ 1,511 $ 9,385 $ — $ 10,896 Trading commodity derivative assets 101 430 — 531 Total commodity derivative assets $ 1,612 $ 9,815 $ — $ 11,427 Non-trading commodity derivative liabilities $ — $ (661 ) $ — $ (661 ) Trading commodity derivative liabilities — (87 ) — (87 ) Total commodity derivative liabilities $ — $ (748 ) $ — $ (748 ) Contingent payment arrangement $ — $ — $ (22,653 ) $ (22,653 ) The Company had no transfers of assets or liabilities between any of the above levels during the years ended December 31, 2017 , 2016 and 2015 . The Company’s derivative contracts include exchange-traded contracts fair valued utilizing readily available quoted market prices and non-exch ange-traded contra cts fair valued using market price quotations available through brokers or over-the-counter and on-line exchanges. In addition, in determining the fair value of the Company’s derivative contracts, the Company applies a credit risk valuation adjustment to reflect credit risk, which is calculated based on the Company’s or the counterparty’s historical credit risks. As of December 31, 2017 and 2016 , the credit risk valuation adjustment was not material. The contingent payment arrangements referred to above reflect estimated earnout obligations incurred in relation to the Company's acquisitions. As of December 31, 2017 , the estimated earnout obligations were $4.6 million , which was comprised of the Major Earnout and the Stock Earnout in the amount of $4.6 million , and zero , respectively. The final Provider Earnout payment was paid in June 2017. The Verde Earnout was settled for $5.9 million on January 12, 2018 with a promissory note payable to the Seller in June 2019 and is classified as long-term debt as of December 31, 2017 . As of December 31, 2016 , the estimated earnout obligations were $22.7 million , which was comprised of the Provider Earnout, the Major Earnout and the Stock Earnout in the amount of $4.9 million , $17.1 million , and $0.7 million , respectively. As of December 31, 2017 , the estimated earnouts are recorded on our consolidated balance sheets in current liabilities - contingent consideration and long-term liabilities - contingent consideration in the amount of $4.0 million and $0.6 million respectively; and as of December 31, 2016 , in current liabilities - contingent consideration and long-term liabilities - contingent consideration in the amount of $11.8 million and $10.8 million , respectively. The Provider Earnout, the Major Earnout, and the Verde Earnout are discussed in Note 3 "Acquisitions." The CenStar Earnout was based on a financial measurement attributable to the operations of CenStar for the year following the closing of the acquisition. In determining the fair value of the CenStar Earnout, the Company forecasted a one year performance measurement, as defined by the CenStar stock purchase agreement. As this calculation was based on management's estimates of the liability, we had classified the CenStar Earnout as a Level 3 measurement. During the first quarter of 2016, our estimate of the CenStar Earnout was increased to $1.5 million , which was based on the results of operations during such period. In August 2016, we entered into a settlement and release agreement with the seller of CenStar in which the Company paid $1.3 million to such seller and released an additional $0.6 million from escrow in full satisfaction of the earnout obligation under the CenStar stock purchase agreement. During the year ended December 31, 2016, the remaining estimated earnout liability of $0.2 million was written off via a reduction to general and administrative expense in our consolidated statements of operations. The Provider Earnout was based on achievement by the Provider Companies of a certain customer count criteria over the nine month period following the closing of the Provider Companies acquisition. The sellers of the Provider Companies were entitled to a maximum of $9.0 million and a minimum of $5.0 million in earnout payments based on the level of customer count attained, as defined by the Provider Companies membership interest purchase agreement. In March and June 2017, the Company paid the sellers of the Provider Companies $1.0 million and $4.5 million , respectively, related to the earnout based on the achievement of certain customer count and sales targets. During the year ended December 31, 2017 , the Company recorded accretion of $0.1 million to reflect the impact of the time value of the liability prior to the final payment in June 2017. The Company additionally recorded $0.5 million of general and administrative expense related to the change in fair value of the earnout prior to the final payment in June 2017. During the period from August 1, 2016 (acquisition date) through December 31, 2016, the Company recorded accretion of $0.1 million to reflect the impact of the time value of the liability. In determining the fair value of the Provider Earnout, the Company forecasted an expected customer count and certain other related criteria and calculated the probability of such forecast being attained. As this calculation was based on management's estimates of the liability, we classified the Provider Earnout as a Level 3 measurement. The Major Earnout is based on the achievement by the Major Energy Companies of certain performance targets over the 33 month period following NG&E's closing of the Major Energy Companies acquisition (i.e., April 15, 2016). The previous members of Major Energy Companies are entitled to a maximum of $20.0 million in earnout payments based on the level of performance targets attained, as defined by the Major Purchase Agreement. The Stock Earnout obligation is contingent upon the Major Energy Companies achieving the Major Earnout's performance target ceiling, thereby earning the maximum Major Earnout payments. If the Major Energy Companies earn such maximum Major Earnout payments, NG&E would be entitled to a maximum of 400,000 shares of Class B common stock (and a corresponding number of Spark HoldCo units). In determining the fair value of the Major Earnout and the Stock Earnout, the Company forecasted certain expected performance targets and calculated the probability of such forecast being attained. In March 2017, the Company paid the previous members of the Major Energy Companies $7.4 million related to the period from April 15, 2016 through December 31, 2016. During the year ended December 31, 2017 , the Company recorded accretion of $3.8 million to reflect the impact of the time value of the liability. The Company revalued the liability at December 31, 2017 , resulting in the decrease of the fair value of the liability to $4.6 million . During the period from April 15, 2016 (NG&E acquisition date) through December 31, 2016, the Company recorded accretion of $5.0 million to reflect the impact of the time value of the liability. The Company revalued the liability at December 31, 2016, resulting in the write-down of the fair value of the liability to $17.8 million . The impact of the $9.6 million and $1.1 million decrease in fair value is recorded in general and administrative expenses for the years ended December 31, 2017 and 2016 , respectively. As this calculation is based on management's estimates of the liability, we classified the Major Earnout as a Level 3 measurement. The Verde Earnout was based on achievement by the Verde Companies of certain performance targets over the 18 month period following the closing of the acquisition of the Verde Companies. The Verde Earnout was valued at $5.4 million as of July 1, 2017, the acquisition date. The Company and the Seller agreed to terminate the Verde Earnout on January 12, 2018, and settled the obligation with the issuance of a $5.9 million promissory note payable due to the Seller in June 2019 (the “Verde Earnout Termination Note”). The Company recorded a $0.3 million increase in fair value of the Verde Earnout in general and administrative expenses and classified the liability as long-term debt as of December 31, 2017 . During the year ended December 31, 2017 , the Company recorded accretion of $0.2 million to reflect the impact of the time value of the liability. In determining the fair value of the Verde Earnout, the Company forecasted certain expected performance targets and calculated the probability of such forecast being attained. As the calculation was based on management's estimates of the liability, we classified the Verde Earnout liability as a Level 3 measurement prior to settlement. See discussion of the Verde Earnout Termination Note in Note 8 "Debt." The following tables present reconciliations of liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the years ended December 31, 2017 and 2016 , respectively. CenStar Earnout Major Earnout and Stock Earnout Provider Earnout Verde Earnout Total Fair Value at December 31, 2015 $ 500 $ — $ — $ — $ 500 Purchase price contingent consideration $ — $ 13,910 $ 4,823 $ — 18,733 Change in fair value of contingent consideration, net 843 (1,140 ) — — (297 ) Accretion of contingent earnout consideration (included within interest expense) — 4,990 70 — 5,060 Payments and settlements (1) (1,343 ) — — — (1,343 ) Fair Value at December 31, 2016 $ — $ 17,760 $ 4,893 $ — $ 22,653 Purchase price consideration $ — $ — $ — $ 5,400 $ 5,400 Change in fair value of contingent consideration, net — (9,555 ) 500 347 (8,708 ) Accretion of contingent earnout consideration (included within interest expense) — 3,848 107 153 4,108 Payments and settlements (1) — (7,403 ) (5,500 ) (5,900 ) (18,803 ) Fair Value at December 31, 2017 $ — $ 4,650 $ — $ — $ 4,650 (1) Payments and settlements include pay downs at maturity and the termination of the Verde Earnout liability, which was replaced with the Verde Earnout Termination Note. See discussion above and in Note 8 "Debt." Assets and Liabilities Measured at Fair Value on a Non-recurring Basis We apply the provisions of the fair value measurement standard to our non-recurring, non-financial measurements including business combinations as well as impairment related to goodwill and other long-lived assets. For business combinations (see Note 3 "Acquisitions" ), the purchase price is allocated to the assets acquired and liabilities assumed based on a discounted cash flow model for most intangibles as well as market assumptions for the valuation of equipment and other fixed assets. We utilize a discounted cash flow model in evaluating impairment considerations related to goodwill and long-lived assets. Given the unobservable nature of the inputs, the discounted cash flow models are considered to use Level 3 inputs.

Accounting for Derivative Instr

Accounting for Derivative Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Accounting for Derivative Instruments	10. Accounting for Derivative Instruments The Company is exposed to the impact of market fluctuations in the price of electricity and natural gas and basis costs, storage and ancillary capacity charges from independent system operators. The Company uses derivative instruments to manage exposure to these risks, and historically designated certain derivative instruments as cash flow hedges for accounting purposes. The Company holds certain derivative instruments that are not held for trading purposes and are not designated as hedges for accounting purposes. These derivative instruments represent economic hedges that mitigate the Company’s exposure to fluctuations in commodity prices. For these derivative instruments, changes in the fair value are recognized currently in earnings in retail revenues or retail cost of revenues. As part of the Company’s strategy to optimize its assets and manage related risks, it also manages a portfolio of commodity derivative instruments held for trading purposes. The Company’s commodity trading activities are subject to limits within the Company’s Risk Management Policy. For these derivative instruments, changes in the fair value are recognized currently in earnings in net asset optimization revenues. Derivative assets and liabilities are presented net in the Company’s consolidated balance sheets when the derivative instruments are executed with the same counterparty under a master netting arrangement. The Company’s derivative contracts include transactions that are executed both on an exchange and centrally cleared, as well as over-the-counter, bilateral contracts that are transacted directly with a third party. To the extent the Company has paid or received collateral related to the derivative assets or liabilities, such amounts would be presented net against the related derivative asset or liability’s fair value. As of December 31, 2017 and 2016 , the Company had paid $0.1 million and zero in collateral outstanding, respectively. The specific types of derivative instruments the Company may execute to manage the commodity price risk include the following: • Forward contracts, which commit the Company to purchase or sell energy commodities in the future; • Futures contracts, which are exchange-traded standardized commitments to purchase or sell a commodity or financial instrument; • Swap agreements, which require payments to or from counterparties based upon the differential between two prices for a predetermined notional quantity; and, • Option contracts, which convey to the option holder the right but not the obligation to purchase or sell a commodity. The Company has entered into other energy-related contracts that do not meet the definition of a derivative instrument and are therefore not accounted for at fair value including the following: • Forward electricity and natural gas purchase contracts for retail customer load; and, • Natural gas transportation contracts and storage agreements. Volumetric Underlying Derivative Transactions The following table summarizes the net notional volume buy/(sell) of the Company’s open derivative financial instruments accounted for at fair value, broken out by commodity, as of (in thousands): Non-trading Commodity Notional December 31, 2017 December 31, 2016 Natural Gas MMBtu 9,191 8,016 Natural Gas Basis MMBtu — — Electricity MWh 8,091 3,958 Trading Commodity Notional December 31, 2017 December 31, 2016 Natural Gas MMBtu 26 (953 ) Natural Gas Basis MMBtu (225 ) (380 ) Gains (Losses) on Derivative Instruments Gains (losses) on derivative instruments, net and current period settlements on derivative instruments were as follows for the periods indicated (in thousands): Year Ended December 31, 2017 2016 2015 Gain (loss) on non-trading derivatives, net 5,588 22,254 (18,423 ) (Loss) gain on trading derivatives, net (580 ) 153 (74 ) Gain (loss) on derivatives, net $ 5,008 $ 22,407 $ (18,497 ) Current period settlements on non-trading derivatives (1) (2) (3) (4) 16,508 (2,284 ) 20,279 Current period settlements on trading derivatives (199 ) 138 268 Total current period settlements on derivatives (1) (2) (3) (4) $ 16,309 $ (2,146 ) $ 20,547 (1) Excludes settlements of less than $0.1 million , $1.0 million and $3.4 million , respectively, for the years ended December 31, 2017 , 2016 , and 2015 related to non-trading derivative liabilities assumed in the acquisitions of CenStar and Oasis. (2) Excludes settlements of $0.5 million and $25.6 million , respectively, for the years ended December 31, 2017 and 2016 related to non-trading derivative liabilities assumed in the acquisitions of Provider Companies and Major Energy Companies. (3) Excludes settlements of $1.1 million for the year ended December 31, 2017 related to non-trading derivative liabilities assumed in the acquisitions of Perigee and other customers. (4) Excludes settlements of $1.7 million for the year ended December 31, 2017 related to non-trading derivative liabilities assumed in the acquisition of the Verde Companies. Gains (losses) on trading derivative instruments are recorded in net asset optimization revenues, and gains (losses) on non-trading derivative instruments are recorded in retail cost of revenues on the consolidated statements of operations. Fair Value of Derivative Instruments The following tables summarize the fair value and offsetting amounts of the Company’s derivative instruments by counterparty and collateral received or paid as of (in thousands): December 31, 2017 Description Gross Assets Gross Net Assets Cash Net Amount Non-trading commodity derivatives $ 60,167 $ (29,432 ) $ 30,735 $ — $ 30,735 Trading commodity derivatives 918 (462 ) 456 — 456 Total Current Derivative Assets 61,085 (29,894 ) 31,191 — 31,191 Non-trading commodity derivatives 16,055 (12,746 ) 3,309 — 3,309 Trading commodity derivatives — — — — — Total Non-current Derivative Assets 16,055 (12,746 ) 3,309 — 3,309 Total Derivative Assets $ 77,140 $ (42,640 ) $ 34,500 $ — $ 34,500 December 31, 2017 Description Gross Gross Net Cash Net Amount Non-trading commodity derivatives $ (4,517 ) $ 3,059 $ (1,458 ) $ 65 $ (1,393 ) Trading commodity derivatives (517 ) 273 (244 ) — (244 ) Total Current Derivative Liabilities (5,034 ) 3,332 (1,702 ) 65 (1,637 ) Non-trading commodity derivatives (676 ) 732 56 56 Trading commodity derivatives (566 ) 18 (548 ) — (548 ) Total Non-current Derivative Liabilities (1,242 ) 750 (492 ) — (492 ) Total Derivative Liabilities $ (6,276 ) $ 4,082 $ (2,194 ) $ 65 $ (2,129 ) December 31, 2016 Description Gross Assets Gross Net Assets Cash Net Amount Non-trading commodity derivatives $ 19,657 $ (11,844 ) $ 7,813 $ — $ 7,813 Trading commodity derivatives 614 (83 ) 531 — 531 Total Current Derivative Assets 20,271 (11,927 ) 8,344 — 8,344 Non-trading commodity derivatives 7,874 (4,791 ) 3,083 — 3,083 Total Non-current Derivative Assets 7,874 (4,791 ) 3,083 — 3,083 Total Derivative Assets $ 28,145 $ (16,718 ) $ 11,427 $ — $ 11,427 December 31, 2016 Description Gross Gross Net Cash Net Amount Non-trading commodity derivatives $ (662 ) $ 69 $ (593 ) $ (593 ) Trading commodity derivatives (92 ) 5 (87 ) — (87 ) Total Current Derivative Liabilities (754 ) 74 (680 ) — (680 ) Non-trading commodity derivatives (305 ) 237 (68 ) — (68 ) Total Non-current Derivative Liabilities (305 ) 237 (68 ) — (68 ) Total Derivative Liabilities $ (1,059 ) $ 311 $ (748 ) $ — $ (748 )

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	11. Stock-Based Compensation Restricted Stock Units In connection with the IPO, the Company adopted the Spark Energy, Inc. Long-Term Incentive Plan for the employees, consultants and directors of the Company and its affiliates who perform services for the Company. The Long-Term Incentive Plan was amended and restated on September 1, 2016 (as amended and restated, the "LTIP"). The purpose of the LTIP is to provide a means to attract and retain individuals to serve as directors, employees and consultants who provide services to the Company by affording such individuals a means to acquire and maintain ownership of awards, the value of which is tied to the performance of the Company’s Class A common stock. The LTIP provides for grants of cash payments, stock options, stock appreciation rights, restricted stock or units, bonus stock, dividend equivalents, and other stock-based awards with the total number of shares of stock available for issuance under the LTIP not to exceed 2,750,000 shares. Periodically the Company grants restricted stock units to our officers, employees, non-employee directors and certain employees of our affiliates who perform services for the Company. The restricted stock unit awards vest over approximately one year for non-employee directors and ratably over approximately three or four years for officers, employees, and employees of affiliates, with the initial vesting date occurring in May of the subsequent year. Each restricted stock unit is entitled to receive a dividend equivalent when dividends are declared and distributed to shareholders of Class A common stock. These dividend equivalents shall be retained by the Company, reinvested in additional restricted stock units effective as of the record date of such dividends and vested upon the same schedule as the underlying restricted stock unit. In accordance with ASC 718, Compensation - Stock Compensation (“ASC 718”) , the Company measures the cost of awards classified as equity awards based on the grant date fair value of the award, and the Company measures the cost of awards classified as liability awards at the fair value of the award at each reporting period. The Company has utilized an estimated 6% annual forfeiture rate of restricted stock units in determining the fair value for all awards excluding those issued to executive level recipients and non-employee directors, for which no forfeitures are estimated to occur. The Company has elected to recognize related compensation expense on a straight-line basis over the associated vesting periods. Although the restricted stock units allow for cash settlement of the awards at the sole discretion of management of the Company, management intends to settle the awards by issuing shares of the Company’s Class A common stock. Total stock-based compensation expense for the years ended December 31, 2017 , 2016 and 2015 was $5.1 million , $5.2 million and $3.2 million . Total income tax benefit related to stock-based compensation recognized in net income (loss) was $2.1 million , $2.1 million and $1.2 million for the years ended December 31, 2017 , 2016 and 2015 . Equity Classified Restricted Stock Units Restricted stock units issued to employees and officers of the Company are classified as equity awards. The fair value of the equity classified restricted stock units is based on the Company’s Class A common stock price as of the grant date. The Company recognized stock based compensation expense of $2.8 million , $2.3 million and $2.2 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, in general and administrative expense with a corresponding increase to additional paid in capital. The following table summarizes equity classified restricted stock unit activity and unvested restricted stock units for the year ended December 31, 2017 : Number of Shares (in thousands) Weighted Average Grant Date Fair Value Unvested at December 31, 2016 526 $ 9.56 Granted 307 18.10 Dividend reinvestment issuances 27 15.64 Vested (180 ) 17.88 Forfeited (40 ) 13.27 Unvested at December 31, 2017 640 $ 11.56 For the year ended December 31, 2017 , 179,628 restricted stock units vested, with 118,514 shares of Class A common stock distributed to the holders of these units and 61,114 shares of Class A common stock withheld by the Company to cover taxes owed on the vesting of such units. As of December 31, 2017 , there was $7.4 million of total unrecognized compensation cost related to the Company’s equity classified restricted stock units, which is expected to be recognized over a weighted average period of approximately 2.9 years. Liability Classified Restricted Stock Units Restricted stock units issued to non-employee directors of the Company and employees of certain of our affiliates are classified as liability awards in accordance with ASC 718 as the awards are either to a) non-employee directors that allow for the recipient to choose net settlement for the amount of withholding taxes dues upon vesting or b) to employees of certain affiliates of the Company and are therefore not deemed to be employees of the Company. The fair value of the liability classified restricted stock units is based on the Company’s Class A common stock price as of the reported period ending date. The Company recognized stock based compensation expense of $2.3 million and $3.0 million and $1.0 million for years ended December 31, 2017 , 2016 and 2015 , respectively, in general and administrative expense with a corresponding increase to liabilities. As of December 31, 2017 , the Company’s liabilities related to these restricted stock units recorded in current liabilities was $0.7 million . As of December 31, 2016 , the Company's liabilities related to these restricted stock units recorded in current liabilities was $1.5 million . The following table summarizes liability classified restricted stock unit activity and unvested restricted stock units for the year ended December 31, 2017 : Number of Shares (in thousands) Weighted Average Reporting Date Fair Value Unvested at December 31, 2016 252 $ 15.15 Granted 140 12.40 Dividend reinvestment issuances 10 12.40 Vested (176 ) 16.93 Forfeited (2 ) 12.40 Unvested at December 31, 2017 224 $ 12.40 For the year ended December 31, 2017 , 176,386 restricted stock units vested, with 123,451 shares of Class A common stock distributed to the holders of these units and 52,935 shares of Class A common stock withheld by the Company to cover taxes owed on the vesting of such units. As of December 31, 2017 , there was $1.8 million of total unrecognized compensation cost related to the Company’s liability classified restricted stock units, which is expected to be recognized over a weighted average period of approximately 2.5 years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes The Company, CenStar and Verde Energy USA, Inc. (Verde Corp) are each subject to U.S. federal income tax as corporations. CenStar and Verde Corp will file consolidated tax returns in jurisdictions that allow combined reporting. Spark HoldCo and its subsidiaries, with the exception of CenStar and Verde Corp, are treated as flow-through entities for U.S. federal income tax purposes, and, as such, are generally not subject to U.S. federal income tax at the entity level. Rather, the tax liability with respect to their taxable income is passed through to their members or partners. Accordingly, the Company is subject to U.S. federal income taxation on its allocable share of Spark HoldCo's net U.S. taxable income. The Company reports federal and state income taxes for its share of the partnership income attributable to its ownership in Spark HoldCo and for the income taxes attributable to CenStar, a C-corporation, which is owned by Spark HoldCo. The income tax liability for the partnership does not accrue to the partnership, but rather the investors are responsible for the income taxes based upon the investor's share of the partnership's income. Net income attributable to the non-controlling interest in CenStar includes the provision for income taxes. The Company accounts for income taxes using the assets and liabilities method. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and the tax bases of the assets and liabilities. The Company applies existing tax law and the tax rate that the Company expects to apply to taxable income in the years in which those differences are expected to be recovered or settled in calculating the deferred tax assets and liabilities. Effects of changes in tax rates on deferred tax assets and liabilities are recognized in income in the period of the tax rate enactment. A valuation allowance is recorded when it is not more likely than not that some or all of the benefit from the deferred tax asset will be realized. On December 22, 2017, the President signed the Tax Cuts and Jobs Act (“U.S. Tax Reform”), which enacts a wide range of changes to the U.S. Corporate income tax system. The impact of U.S. Tax Reform primarily represents our estimates of revaluing our U.S. deferred tax assets and liabilities based on the rates at which they are expected to be recognized in the future. For U.S. federal purposes the corporate statutory income tax rate was reduced from 35% to 21% , effective for the 2018 tax year. Based on our historical financial performance, at December 31, 2017 we have a significant net deferred tax asset position that we have remeasured at the lower corporate rate of 21% and recognized a tax expense to adjust net deferred tax assets to the reduced value. The provision for income taxes included the following components: (in thousands) 2017 2016 2015 Current: Federal $ 6,992 $ 5,361 $ 268 State 1,952 1,683 (277 ) Total Current 8,944 7,044 (9 ) Deferred: Federal 26,583 2,944 1,820 State 2,001 438 163 Total Deferred 28,584 3,382 1,983 Provision for income taxes $ 37,528 $ 10,426 $ 1,974 The effective income tax rate was 33.0% and 13.7% for the years ended December 31, 2017 and 2016 , respectively. The following table reconciles the income tax benefit included in the consolidated statement of operations with income tax expense that would result from application of the statutory federal tax rate, 35% for the years ended December 31, 2017 and 2016 , respectively, to loss before income tax expense (benefit): (in thousands) 2017 2016 Expected provision at federal statutory rate $ 39,833 $ 26,635 Increase (decrease) resulting from: Impact of U.S. Tax Reform 13,217 — Non-controlling interest (19,810 ) (17,740 ) State income taxes, net of federal income tax effect 2,569 1,346 Other 1,719 185 Provision for income taxes $ 37,528 $ 10,426 Total income tax expense for the year ended December 31, 2017 differed from amounts computed by applying the U.S. federal statutory tax rates to pre-tax income primarily due to state taxes and the impact of permanent differences between book and taxable income, most notably the income attributable to non-controlling interest. The effective tax rate includes a rate benefit attributable to the fact that Spark HoldCo operates as a limited liability company treated as a partnership for federal and state income tax purposes and is not subject to federal and state income taxes. Accordingly, the portion of earnings attributable to non-controlling interest is subject to tax when reported as a component of the non-controlling interest’s taxable income. The effective rate in 2017 includes a $13.2 million unfavorable impact resulting from the enactment of U.S. Tax Reform. The primary impact of the change in tax law was the remeasurment of our U.S. federal deferred tax assets and liabilities at the tax rate expected to be applied when the temporary differences are settled at a rate of 21% . The Company accounts for income taxes using the assets and liabilities method. Deferred tax assets and liabilities are recognized for future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and those assets and liabilities tax bases. The Company applies existing tax law and the tax rate that the Company expects to apply to taxable income in the years in which those differences are expected to be recovered or settled in calculating the deferred tax assets and liabilities. Effects of changes in tax rates on deferred tax assets and liabilities are recognized in income in the period of the tax rate enactment. We remeasured our deferred tax assets and liabilities, excluding those that will be included on our 2017 tax return based on the rates we expect to realize the deferred tax assets and liabilities at in the future. The amount that was recorded related to the remeasurement of our deferred tax balance was $13.2 million of tax expense. A valuation allowance is recorded when it is not more likely than not that some or all of the benefit from the deferred tax asset will be realized. The components of the Company’s deferred tax assets as of December 31, 2017 and 2016 are as follows: (in thousands) 2017 2016 Deferred Tax Assets: Investment in Spark HoldCo $ 18,340 $ 35,359 Benefit of TRA Liability 8,175 19,705 Federal net operating loss carryforward 660 2,076 State net operating loss carryforward 166 366 Total deferred tax assets 27,341 57,506 Deferred Tax Liabilities: Derivative liabilities (811 ) (1,849 ) Intangibles (2,287 ) (1,519 ) Property and equipment — (10 ) Other (58 ) (19 ) Total deferred tax liabilities (3,156 ) (3,397 ) Total deferred tax assets/liabilities $ 24,185 $ 54,109 On the IPO date, the Company recorded a net deferred tax asset of $15.6 million related to the step up in tax basis resulting from the purchase by the Company of Spark HoldCo units from NuDevco. In addition, the Company had a long-term liability of $20.7 million to record the effect of the Tax Receivable Agreement liability and a corresponding long-term deferred tax asset of $7.9 million . As of December 31, 2017 and 2016 , the Company had a total liability of $32.3 million and $49.9 million , respectively, for the effect of the Tax Receivable Agreement liability. The Company adjusted the Tax Receivable Agreement liability at December 31, 2017 to include the 2016 tax returns filed. The adjustment resulted in an increase to the liability of $4.7 million , of which $1.8 million increased the deferred tax asset and $2.9 million decreased equity. On December 22, 2017, the President signed the Tax Cuts and Jobs Act (“U.S. Tax Reform”), which enacts a wide range of changes to the U.S. Corporate income tax system including a reduction in the U.S. corporate tax rate to 21% effective in 2018. The revised corporate income tax rate reduces the amount of net cash savings to be realized in future periods. Therefore, we have reduced the TRA liability as of December 31, 2017 by $22.3 million to reflect the effect of U.S. Tax Reform and recorded this adjustment through Other Income. The Company had a long-term deferred tax asset of approximately $8.2 million related to the Tax Receivable Agreement liability at December 31, 2017 . See Note 14 "Transactions with Affiliates" for further discussion. The Company has a federal net operating loss carry forward totaling $3.8 million expiring in 2037 and a state net operating loss of $4.1 million expiring through 2037. No valuation allowance has been recorded as management believes that there will be sufficient future taxable income to fully utilize deferred tax assets. The Company periodically assesses whether it is more likely than not that it will generate sufficient taxable income to realize its deferred income tax assets. In making this determination, the Company considers all available positive and negative evidence and makes certain assumptions. The Company considers, among other things, its deferred tax liabilities, the overall business environment, its historical earnings and losses, current industry trends, and its outlook for future years. The Company believes it is more likely than not that the deferred tax assets will be utilized. On February 3, 2016, Retailco exchanged 2,000,000 of its Spark HoldCo units (together with a corresponding number of shares of Class B common stock) for shares of Class A common stock. The exchange resulted in a step up in tax basis, which gave rise to a deferred tax asset of approximately $8.0 million on the exchange date. In addition, the Company recorded an additional long-term liability as a result of the exchange of approximately $10.3 million pursuant to the Tax Receivable Agreement and a corresponding long-term deferred tax asset of approximately $3.9 million . The initial estimate for the deferred tax asset, net of the liability, under the Tax Receivable Agreement was recorded within additional paid-in capital on our consolidated balance sheet at December 31, 2017 . On April 1, 2016, Retailco exchanged 3,450,000 of its Spark HoldCo units (together with a corresponding number of shares of Class B common stock) for shares of Class A common stock. The exchange resulted in a step up in tax basis, which gave rise to a deferred tax asset of approximately $7.6 million on the exchange date. In addition, the Company recorded an additional long-term liability as a result of the exchange of approximately $10.3 million pursuant to the Tax Receivable Agreement and a corresponding long-term deferred tax asset of approximately $3.9 million . The initial estimate for the deferred tax asset, net of the liability, under the Tax Receivable Agreement was recorded within additional paid-in capital on our consolidated balance sheet at December 31, 2017 . On June 8, 2016, Retailco exchanged 1,000,000 of its Spark HoldCo units (together with a corresponding number of shares of Class B common stock) for shares of Class A common stock. The exchange resulted in a step up in tax basis, which gave rise to a deferred tax asset of approximately $5.3 million on the exchange date. In addition, the Company recorded an additional long-term liability as a result of the exchange of approximately $6.9 million pursuant to the Tax Receivable Agreement and a corresponding long-term deferred tax asset of approximately $2.6 million . The initial estimate for the deferred tax asset, net of the liability, under the Tax Receivable Agreement was recorded within additional paid-in capital on our consolidated balance sheet at December 31, 2017 . Separate federal and state income tax returns are filed for Spark Energy, Inc. and Spark HoldCo. CenStar owns all the outstanding stock of Verde Corp and both are taxed as corporations. CenStar and Verde will file a federal consolidated return for 2017 and separate state income tax returns in the states that do not allow combined reporting. The tax years 2013 through 2016 remain open to examination by the major taxing jurisdictions to which the Company is subject to income tax. NuDevco would be responsible for any audit adjustments incurred in connection with transactions occurring up to July 31, 2014 for Spark Energy, Inc. and Spark HoldCo. The last closed audit period of exam was for the 2011 Spark Energy, LLC’s federal tax return and resulted in no adjustments by the IRS. Spark Energy, Inc., Spark HoldCo, ,CenStar, and Verde Corp are not currently under any income tax audits. Accounting for uncertainty in income taxes prescribes a recognition threshold and measurement methodology for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. As of December 31, 2017 and 2016 there was no liability, and for the years ended December 31, 2017 , 2016 and 2015 , there was no expense recorded for interest and penalties associated with uncertain tax positions or unrecognized tax positions. Additionally, the Company does no t have unrecognized tax benefits as of December 31, 2017 and 2016 .

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. Commitment and Contingencies From time to time, the Company may be involved in legal, tax, regulatory and other proceedings in the ordinary course of business. Other than proceedings discussed below, management does not believe that we are a party to any litigation, claims or proceedings that will have a material impact on the Company’s consolidated financial condition or results of operations. Liabilities for loss contingencies arising from claims, assessments, litigations or other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. Indirect Tax Audits The Company is undergoing various types of indirect tax audits spanning from years 2009 to 2017 for which the Company may have additional liabilities arise. At the time of filing these consolidated financial statements, these indirect tax audits are at an early stage and subject to substantial uncertainties concerning the outcome of audit findings and corresponding responses. As of December 31, 2017 , we have accrued of $1.7 million related to indirect tax audits. The outcome of these indirect tax audits may result in additional expense. Legal Proceedings The Company is the subject of the following lawsuits. At the time of filing these consolidated financial statements, this litigation is at an early stage and subject to substantial uncertainties concerning the outcome of material factual and legal issues. Accordingly, we cannot currently predict the manner and timing of the resolution of this litigation or estimate a range of possible losses or a minimum loss that could result from an adverse verdict in a potential lawsuit. John Melville et al v. Spark Energy Inc. and Spark Energy Gas, LLC is a purported class action filed on December 17, 2015 in the United States District Court for the District of New Jersey alleging, among other things, that (i) sales representatives engaged as independent contractors for Spark Energy Gas, LLC engaged in deceptive acts in violation of the New Jersey Consumer Fraud Act, and (ii) Spark Energy Gas, LLC breached its contract with plaintiff, including a breach of the covenant of good faith and fair dealing. On September 5, 2017, the parties reached a confidential settlement in this matter, which the Company expensed and paid in the fourth quarter of 2017. Halifax-American Energy Company, LLC et al v. Provider Power, LLC, Electricity N.H., LLC, Electricity Maine, LLC, Emile Clavet and Kevin Dean is a lawsuit initially filed on June 12, 2014, in the Rockingham County Superior Court, State of New Hampshire, alleging various claims related to the Provider Companies’ employment of a sales contractor formerly employed with one or more of the plaintiffs, including misappropriation of trade secrets and tortious interference with a contractual relationship. The relief sought included compensatory and punitive damages and attorney's fees. The dispute occurred prior to the Company's acquisition of the Provider Companies. Portions of the original claim proceeded to trial and on January 19, 2016, a jury found in favor of the plaintiffs. Damages totaling approximately $0.6 million and attorneys' fees totaling approximately $0.3 million were awarded to the plaintiffs. On May 4, 2016, following post-verdict motions, the defendants filed an appeal in the State of New Hampshire Supreme Court, appealing, among other things the failure of the trial court to direct a verdict for the defendants, to set aside the verdict, or grant judgment for the defendants, and the trial court's award of certain attorneys' fees. The appellate hearing was held on June 1, 2017. The New Hampshire Supreme Court decided the appeal on February 9, 2018, upholding the jury's verdict and the trial court's rulings in all respects. As of December 31, 2017 , the Company has accrued approximately $1.0 million in contingent liabilities related to this litigation. Initial damages and attorneys' fees have been factored into the purchase price for the Provider Companies, and the Company believes it has full indemnity coverage for any actual exposure in this appeal. Katherine Veilleux and Jennifer Chon, individually and on behalf of all other similarly situated v. Electricity Maine. LLC, Provider Power, LLC, Spark HoldCo, LLC, Kevin Dean and Emile Clavet is a purported class action lawsuit filed on November 18, 2016 in the United States District Court of Maine, alleging that Electricity Maine, LLC, an entity acquired by Spark HoldCo, LLC in mid-2016, enrolled and re-enrolled customers through fraudulent and misleading advertising, promotions, and other communications prior to the acquisition. Plaintiffs further allege that some improper enrollment and re-enrollment practices have continued to the present date. Plaintiffs allege the following claims against all defendants: violation of the Maine Unfair Trade Practices Act, violation of RICO, negligence, negligent misrepresentation, fraudulent misrepresentation, unjust enrichment and breach of contract. Plaintiffs seek unspecified damages for themselves and the purported class, rescission of contracts with Electricity Maine, injunctive relief, restitution, and attorney’s fees. By order dated November 15, 2017, the Court, pursuant to Rule 12(b)(6), dismissed all claims against Spark HoldCo except the claims for violation of the Maine Unfair Trade Practices Act and for unjust enrichment. Discovery limited to issues relevant to class certification under Rule 23 of the Federal Rules of Civil Procedure has just begun. Spark HoldCo intends to vigorously defend this matter and the allegations asserted therein, including the request to certify a class. Given the early stages of this matter, we cannot predict the outcome or consequences of this case at this time. The Company believes it is fully indemnified for this litigation matter, subject to certain limitations. Gillis et al. v. Respond Power, LLC is a purported class action lawsuit that was originally filed on May 21, 2014 in the Philadelphia Court of Common Pleas. On June 23, 2014, the case was removed to the United States District Court for the Eastern District of Pennsylvania. On September 15, 2014, the plaintiffs filed an amended class action complaint seeking a declaratory judgment that the disclosure statement contained in Respond Power, LLC’s variable rate contracts with Pennsylvania consumers limited the variable rate that could be charged to no more than the monthly rate charged by the consumers’ local utility company. The plaintiffs also allege that Respond Power, LLC (i) breached its variable rate contract with Pennsylvania consumers, and the covenant of good faith and fair dealing therein, by charging rates in excess of the monthly rate charged by the consumers’ local utility company; (ii) engaged in deceptive conduct in violation of the Pennsylvania Unfair Trade Practices and Consumer Protection Law; and (iii) engaged in negligent misrepresentation and fraudulent concealment in connection with purported promises of savings. The amount of damages sought is not specified. By order dated August 31, 2015, the district court denied class certification. The plaintiffs appealed the district court’s denial of class certification to the United States Court of Appeals for the Third Circuit. The United States Court of Appeals for the Third Circuit vacated the district court’s denial of class certification and remanded the matter to the district court for further proceedings. The district court ordered briefing on defendant’s motion to dismiss. Respond Power LLC filed a motion to dismiss the plaintiffs’ declaratory judgment and breach of contract claims (the class claims) on June 30, 2017. The motion is fully briefed and submitted, and the parties are awaiting a decision from the Court. The Company currently cannot predict the outcome or consequences of this case at this time. The Company believes it is fully indemnified for this litigation matter, subject to certain limitations. Jurich v. Verde Energy USA, Inc ., is a purported class action originally filed on March 3, 2015 in the United States District Court for the District of Connecticut and subsequently re-filed on October 8, 2015 in the Superior Court of Judicial District of Hartford, State of Connecticut. The Amended Complaint asserts that the Verde Companies charged rates in violation of its contracts with Connecticut customers and alleges (i) violation of the Connecticut Unfair Trade Practices Act and (ii) breach of the covenant of good faith and fair dealing. Plaintiffs are seeking unspecified actual and punitive damages for the purported class and injunctive relief. The parties have exchanged initial discovery. Plaintiffs’ motion for class certification was briefed and the Verde Companies filed its opposition to plaintiffs’ motion for class certification on October 17, 2017. On December 6, 2017, the Court granted the plaintiffs’ class certification motion. However, the Court opted not to send out class notices, and instead directed the parties to submit briefing on legal issues that could result in a modification or decertification of the class. The parties have proposed to the Court that initial briefing on such motions would be due March 16, 2018. As part of an agreement in connection with the acquisition of the Verde Companies, the original owners of the Verde Companies are handling this matter. Given the early stage of this matter, we cannot predict the outcome or consequences of this case at this time. The Company believes it is fully indemnified for this litigation matter by the original owners of the Verde Companies, subject to certain limitations. Richardson et al v. Verde Energy USA, Inc. is a purported class action filed on November 25, 2015 in the United States District Court for the Eastern District of Pennsylvania alleging that the Verde Companies violated the Telephone Consumer Protection Act by placing marketing calls using an automatic telephone dialing system or a prerecorded voice to the purported class members’ cellular phones without prior express consent and by continuing to make such calls after receiving requests for the calls to cease. Plaintiffs are seeking statutory damages for the purported class and injunctive relief prohibiting Verde Companies' alleged conduct. Discovery on the claims of the named plaintiffs closed on November 10, 2017, and dispositive motions on the named plaintiffs’ claims was filed on November 24, 2017. Plaintiffs’ response to dispositive motions’ pleadings was filed on December 22, 2017 and Verde Companies’ reply briefs were filed on January 5, 2018. To date, no hearing has been set on these motions. As part of an agreement in connection with the acquisition of the Verde Companies, the original owners of the Verde Companies is handling this matter. Given the early stages of this matter, we cannot predict the outcome or consequences of this case at this time. The Company believes it is fully indemnified for this litigation matter by the original owners of the Verde Companies, subject to certain limitations. Coleman v. Verde Energy USA Illinois, LLC is a purported class action filed on January 23, 2017 in the United States District Court for the Southern District of Illinois alleging that the Verde Companies violated the Telephone Consumer Protection Act by placing marketing calls using an automatic telephone dialing system or a prerecorded voice to the purported class members’ cellular phones without prior express consent. The parties have reached a confidential settlement in this matter that was paid in the fourth quarter of 2017. Saul Horowitz, as Sellers’ Representative for the former owners of the Major Energy Companies v. National Gas & Electric, LLC (NG&E) and Spark Energy, Inc. (Spark) , has filed a lawsuit asserting claims of fraudulent inducement against NG&E, breach of contract against NG&E and the Company, and tortious interference with contract against the Company related to the membership interest purchase, subsequent transfer, and associated earnout agreements with the Major Energy Companies' former owners. The relief sought includes unspecified compensatory and punitive damages, prejudgment and post judgment interest, and attorneys’ fees. The lawsuit was filed on October 10, 2017 in the United States District Court for the Southern District of New York, and after the Company and NG&E filed a motion to dismiss, Horowitz filed an Amended Complaint, asserting the same four claims. The Company and NG&E filed a motion to dismiss the fraud and tortious interference claims on January 15, 2018. Briefing on the motion to dismiss concluded on March 1, 2018, and the Court's decision to rule or schedule oral argument is pending as of the date these financial statements are issued. The Company and NG&E deny the allegations asserted and intend to vigorously defend this matter. Given the early stages of this matter, we cannot predict the outcome or consequences of this case at this time.

Transactions with Affiliates

Transactions with Affiliates	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Transactions with Affiliates	14. Transactions with Affiliates The Company enters into transactions with and pays certain costs on behalf of affiliates that are commonly controlled in order to reduce risk, reduce administrative expense, create economies of scale, create strategic alliances and supply goods and services to these related parties. The Company also sells and purchases natural gas and electricity with affiliates. The Company presents receivables and payables with the same affiliate on a net basis in the consolidated balance sheets as all affiliate activity is with parties under common control. Acquisition of Oasis Power Holdings, LLC The acquisition of Oasis by the Company from RAC was a transfer of equity interests of entities under common control on July 31, 2015. Refer to Note 3 "Acquisitions" for further discussion. Acquisition of Major Energy Companies and Perigee The acquisition of Major Energy Companies and Perigee by the Company from NG&E was a transfer of equity interests of entities under common control on August 23, 2016 and April 1, 2017, respectively. Refer to Note 3 "Acquisitions" for further discussion. Master Service Agreement with Retailco Services, LLC We entered into a Master Service Agreement (the “Master Service Agreement”) effective January 1, 2016 with Retailco Services, LLC ("Retailco Services"), which is wholly owned by our Founder. The Master Service Agreement is for a one -year term and renews automatically for successive one -year terms unless the Master Service Agreement is terminated by either party. Retailco Services provides us with operational support services such as: enrollment and renewal transaction services; customer billing and transaction services; electronic payment processing services; customer services and information technology infrastructure and application support services under the Master Service Agreement. See "Cost Allocations" for further discussion of the fees paid in connection with the Master Service Agreement during the year ended December 31, 2017 and 2016 , respectively. Accounts Receivable and Payable — Affiliates The Company recorded current accounts receivable—affiliates of $3.7 million and $2.6 million as of December 31, 2017 and 2016 , respectively, and current accounts payable—affiliates of $4.6 million and $3.8 million as of December 31, 2017 and 2016 , respectively, for certain direct billings and cost allocations for services the Company provided to affiliates, services our affiliates provided to us, and sales or purchases of natural gas and electricity with affiliates. Convertible Subordinated Notes to Affiliate In connection with the financing of the CenStar acquisition, the Company, together with Spark HoldCo, issued the CenStar Note to Retailco Acquisition Co, LLC ("RAC"), which is wholly owned by our Founder, for $2.1 million on July 8, 2015. In connection with the financing of the Oasis acquisition, the Company, together with Spark HoldCo, issued the Oasis Note to RAC for $5.0 million on July 31, 2015. RAC converted the CenStar Note and the Oasis Note into shares of Class B common stock on January 8, 2017 and January 31, 2017, respectively. Refer to Note 8 "Debt" for further discussion. Revenues and Cost of Revenues — Affiliates Cost of revenues—affiliates, recorded in net asset optimization revenues in the consolidated statements of operations for the years ended December 31, 2017 , 2016 and 2015 related to this agreement were $0.1 million , $1.6 million and $11.3 million Revenues—affiliates, recorded in net asset optimization revenues in the consolidated statements of operations for the years ended December 31, 2017 , 2016 and 2015 related to these sales were $1.3 million , $0.2 million , and $1.1 million , respectively. Additionally, the Company entered into a natural gas transportation agreement with another affiliate at its pipeline, whereby the Company transports retail natural gas and pays the higher of (i) a minimum monthly payment or (ii) a transportation fee per MMBtu times actual volumes transported. The current transportation agreement renews annually on February 28 at a fixed rate per MMBtu without a minimum monthly payment. While this transportation agreement remains in effect, this entity is no longer an affiliate as our Founder terminated his interest in the affiliate on May 16, 2016. Cost of revenues —affiliates, recorded in retail cost of revenues in the consolidated statements of operations related to this activity, was zero for the year ended December 31, 2017 and less than $0.1 million for the years ended December 31, 2016 and 2015 , respectively. Cost Allocations The Company paid certain expenses on behalf of affiliates, which are reimbursed by the affiliates to the Company, and our affiliates paid certain expenses on our behalf, which are reimbursed by us. These transactions include costs that can be specifically identified and certain allocated overhead costs associated with general and administrative services, including executive management, due diligence work, recurring management consulting, facilities, banking arrangements, professional fees, insurance, information services, human resources and other support departments to the affiliates. Where costs incurred on behalf of the affiliate or us could not be determined by specific identification for direct billing, the costs were primarily allocated to the affiliated entities or us based on percentage of departmental usage, wages or headcount. The total net amount direct billed and allocated from affiliates w as $25.4 million , $17.0 million and $2.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Of the $25.4 million and $17.0 million total net amount directly billed and allocated from affiliates, the Company recorded general and administrative expense of $22.0 million and $14.7 million for the years ended December 31, 2017 and 2016 , in the consolidated statement of operations in connection with fees paid, net of damages charged, under the Master Service Agreement with Retailco Services. Additionally under the Master Service Agreement, we capitalized $0.7 million and 1.3 million of property and equipment for the application, development and implementation of various systems during the years ended December 31, 2017 and 2016 . The total net amount direct billed and allocated to affiliates was $2.1 million for the year ended December 31, 2015 , which was recorded as a reduction in general and administrative expense in the consolidated statement of operations. Distributions to and Contributions from Affiliates During the years ended December 31, 2017 , 2016 and 2015 , the Company made net capital distributions to NuDevco Retail and Retailco of $15.6 million , $23.7 million and $15.6 million , respectively, in conjunction with the payment of quarterly distributions attributable to its Spark HoldCo units. During the year ended December 31, 2017 and 2016 , respectively, the Company made distributions to NuDevco Retail and Retailco for gross-up distributions of $18.2 million and $11.3 million in connection with distributions made between Spark HoldCo and Spark Energy, Inc. for payment of income taxes incurred by Spark Energy, Inc. Additionally, during the year ended December 31, 2015 the Company received a capital contribution from NuDevco of $0.1 million as NuDevco forgave an account payable due to NuDevco that arose from the payment of withholding taxes related to the vesting of restricted stock units of certain employees of NuDevco who perform services for the Company. Proceeds from Disgorgement of Stockholder Short-swing Profits During the year ended December 31, 2017 and 2016, respectively, the Company recorded $0.7 million and $1.6 million from Retailco for the disgorgement of stockholder short-swing profits under Section 16(b) under the Exchange Act. The amount was recorded as an increase to additional paid-in capital in our consolidated balance sheet as of December 31, 2017 and 2016 . Of the $0.7 million recorded in 2017, the Company received $0.5 million cash during the year ended December 31, 2017 and received $0.2 million cash in February 2018. In addition, the Company received $0.7 million cash during the year ended December 31, 2017 related to the disgorgement of stockholder short-swing profit recorded in our consolidated balance sheet as of December 31, 2016. Class B Common Stock In connection with the Major Energy Companies acquisition, the Company issued RetailCo 4,000,000 shares of Class B common stock (and a corresponding number of Spark HoldCo units) to NG&E. In connection with the financing of the Provider Companies acquisition, the Company sold 1,399,484 shares of Class B common stock (and a corresponding number of Spark HoldCo units) to RetailCo, valued at $14.0 million based on a value of $10 per share. See Note 3 "Acquisitions" for further discussion. Subordinated Debt Facility On December 27, 2016, the Company and Spark HoldCo jointly issued to Retailco, an entity owned by our Founder, a 5% subordinated note in the principal amount of up to $25.0 million . The subordinated note allows the Company and Spark HoldCo to draw advances in increments of no less than $1.0 million per advance up to the maximum principal amount of the subordinated note. The subordinated note matures approximately three and a half years following the date of issuance, and advances thereunder accrue interest at 5% per annum from the date of the advance. The Company has the right to capitalize interest payments under the subordinated note. The subordinated note is subordinated in certain respects to the Company's Senior Credit Facility pursuant to a subordination agreement. The Company may pay interest and prepay principal on the subordinated note so long as it is in compliance with its covenants under the Senior Credit Facility, is not in default under the Senior Credit Facility and has minimum availability of $5.0 million under its borrowing base under the Senior Credit Facility. Payment of principal and interest under the subordinated note is accelerated upon the occurrence of certain change of control or sale transactions. As of December 31, 2017 and 2016 , there were zero and $5.0 million , respectively, in outstanding borrowings under the subordinated note. Tax Receivable Agreement Concurrently with the closing of the IPO, the Company entered into a Tax Receivable Agreement with Spark HoldCo, NuDevco Retail Holdings and NuDevco Retail. This agreement generally provides for the payment by the Company to Retailco, LLC (as the successor to NuDevco Retail Holdings) and NuDevco Retail of 85% of the net cash savings, if any, in U.S. federal, state and local income tax or franchise tax that the Company actually realizes (or is deemed to realize in certain circumstances) in future periods as a result of (i) any tax basis increases resulting from the purchase by the Company of Spark HoldCo units from NuDevco Retail Holdings, (ii) any tax basis increases resulting from the exchange of Spark HoldCo units for shares of Class A common stock pursuant to the Exchange Right (or resulting from an exchange of Spark HoldCo units for cash pursuant to the Cash Option) and (iii) any imputed interest deemed to be paid by the Company as a result of, and additional tax basis arising from, any payments the Company makes under the Tax Receivable Agreement. The Company retains the benefit of the remaining 15% of these tax savings. See Note 12 "Income Taxes" for further discussion. In certain circumstances, the Company may defer or partially defer any payment due (a “TRA Payment”) to the holders of rights under the Tax Receivable Agreement, which are currently Retailco and NuDevco Retail. During the five -year period ending September 30, 2019, the Company will defer all or a portion of any TRA Payment owed pursuant to the Tax Receivable Agreement to the extent that Spark HoldCo does not generate sufficient Cash Available for Distribution (as defined below) during the four-quarter period ending September 30th of the applicable year in which the TRA Payment is to be made in an amount that equals or exceeds 130% (the “TRA Coverage Ratio”) of the Total Distributions (as defined below) paid in such four-quarter period by Spark HoldCo. For purposes of computing the TRA Coverage Ratio: • “Cash Available for Distribution” is generally defined as the Adjusted EBITDA of Spark HoldCo for the applicable period, less (i) cash interest paid by Spark HoldCo, (ii) capital expenditures of Spark HoldCo (exclusive of customer acquisition costs) and (iii) any taxes payable by Spark HoldCo; and • “Total Distributions” are defined as the aggregate distributions necessary to cause the Company to receive distributions of cash equal to (i) the targeted quarterly distribution the Company intends to pay to holders of its Class A common and Series A Preferred Stock payable during the applicable four-quarter period, plus (ii) the estimated taxes payable by the Company during such four-quarter period, plus (iii) the expected TRA Payment payable during the calendar year for which the TRA Coverage Ratio is being tested. In the event that the TRA Coverage Ratio is not satisfied in any calendar year, the Company will defer all or a portion of the TRA Payment to NuDevco Retail or Retailco under the Tax Receivable Agreement to the extent necessary to permit Spark HoldCo to satisfy the TRA Coverage Ratio (and Spark HoldCo is not required to make and will not make the pro rata distributions to its members with respect to the deferred portion of the TRA Payment). If the TRA Coverage Ratio is satisfied in any calendar year, the Company will pay NuDevco Retail or Retailco the full amount of the TRA Payment. Following the five -year deferral period ending September 30, 2019, the Company will be obligated to pay any outstanding deferred TRA Payments to the extent such deferred TRA Payments do not exceed (i) the lesser of the Company’s proportionate share of aggregate Cash Available for Distribution of Spark HoldCo during the five -year deferral period or the cash distributions actually received by the Company during the five -year deferral period, reduced by (ii) the sum of (a) the aggregate target quarterly dividends (which, for the purposes of the Tax Receivable Agreement, will be $0.18125 per Class A common stock share and $0.546875 per Series A Preferred Stock share per quarter) during the five -year deferral period, (b) the Company’s estimated taxes during the five -year deferral period, and (c) all prior TRA Payments and (d) if with respect to the quarterly period during which the deferred TRA Payment is otherwise paid or payable, Spark HoldCo has or reasonably determines it will have amounts necessary to cause the Company to receive distributions of cash equal to the target quarterly distribution payable during that quarterly period. Any portion of the deferred TRA Payments not payable due to these limitations will no longer be payable. We did not meet the threshold coverage ratio required to fund the first payment to Retailco under the Tax Receivable Agreement during the four-quarter period ended September 30, 2015. As such, the initial payment under the Tax Receivable Agreement due in late 2015 was deferred pursuant to the terms thereof. We met the threshold coverage ratio required to fund the second TRA Payment to Retailco and NuDevco Retail under the Tax Receivable Agreement during the four-quarter period ending September 30, 2016, resulting in an initial TRA Payment of $1.4 million becoming due in December 2016. On November 6, 2016, Retailco and NuDevco Retail granted the Company the right to defer the TRA Payment until May 2018. During the period of time when the Company has elected to defer the TRA Payment, the outstanding payment amount will accrue interest at a rate calculated in the manner provided for under the Tax Receivable Agreement. The liability has been classified as current in our consolidated balance sheet at December 31, 2017 . We met the threshold coverage ratio required to fund the third TRA Payment to Retailco and NuDevco Retail under the Tax Receivable Agreement during the four-quarter period ending September 30, 2017. As such, the third payment under the Tax Receivable Agreement due in April 2018 has been classified as current in our consolidated balance sheet at December 31, 2017. We expect to meet the threshold coverage ratio required to fund the fourth payment to Retailco and NuDevco Retail under the Tax Receivable Agreement during the four-quarter period ending September 30, 2018. As such, the fourth payment under the Tax Receivable Agreement due in late 2018 has been classified as current in our consolidated balance sheet at December 31, 2017.

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Reporting	15. Segment Reporting The Company’s determination of reportable business segments considers the strategic operating units under which the Company makes financial decisions, allocates resources and assesses performance of its retail and asset optimization businesses. The Company’s reportable business segments are retail natural gas and retail electricity. The retail natural gas segment consists of natural gas sales to, and natural gas transportation and distribution for, residential and commercial customers. Asset optimization activities, considered an integral part of securing the lowest price natural gas to serve retail gas load, are part of the retail natural gas segment. The Company recorded asset optimization revenues of $178.3 million , $133.0 million and $154.1 million and asset optimization cost of revenues of $179.0 million , $133.6 million and $152.6 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, which are presented on a net basis in asset optimization revenues. The retail electricity segment consists of electricity sales and transmission to residential and commercial customers. Corporate and other consists of expenses and assets of the retail natural gas and retail electricity segments that are managed at a consolidated level such as general and administrative expenses. The acquisitions of CenStar and Oasis in 2015, acquisitions of Major Energy Companies and Provider Energy Companies in 2016, and acquisitions of the Perigee Companies and Verde Companies in 2017 had no impact on our reportable business segments as the portions of those acquisitions related to retail natural gas and retail electricity have been included in those existing business segments. To assess the performance of the Company’s operating segments, the Chief Operating Decision Maker analyzes retail gross margin. The Company defines retail gross margin as operating income (loss) plus (i) depreciation and amortization expenses and (ii) general and administrative expenses, less (i) net asset optimization revenues (expenses), (ii) net gains (losses) on non-trading derivative instruments, and (iii) net current period cash settlements on non-trading derivative instruments. The Company deducts net gains (losses) on non-trading derivative instruments, excluding current period cash settlements, from the retail gross margin calculation in order to remove the non-cash impact of net gains and losses on non-trading derivative instruments. Retail gross margin is a primary performance measure used by our management to determine the performance of our retail natural gas and electricity business by removing the impacts of our asset optimization activities and net non-cash income (loss) impact of our economic hedging activities. As an indicator of our retail energy business’ operating performance, retail gross margin should not be considered an alternative to, or more meaningful than, operating income, as determined in accordance with GAAP. Below is a reconciliation of retail gross margin to income before income tax expense (in thousands): Years Ended December 31, (in thousands) 2017 2016 2015 Reconciliation of Retail Gross Margin to Income before taxes Income before income tax expense $ 113,809 $ 76,099 $ 27,949 Change in Tax Receivable Agreement Liability (22,267 ) — — Interest and other income (256 ) (957 ) (324 ) Interest expense 11,134 8,859 2,280 Operating Income 102,420 84,001 29,905 Depreciation and amortization 42,341 32,788 25,378 General and administrative 101,127 84,964 61,682 Less: Net asset optimization (expenses) revenue (717 ) (586 ) 1,494 Net, Gain (losses) on non-trading derivative instruments 5,588 22,254 (18,423 ) Net, Cash settlements on non-trading derivative instruments 16,508 (2,284 ) 20,279 Retail Gross Margin $ 224,509 $ 182,369 $ 113,615 The Company uses retail gross margin and net asset optimization revenues as the measure of profit or loss for its business segments. This measure represents the lowest level of information that is provided to the chief operating decision maker for our reportable segments. Financial data for business segments are as follows (in thousands): Year Ended December 31, 2017 Retail Retail Corporate Eliminations Spark Retail Total Revenues $ 657,561 $ 140,494 $ — $ — $ 798,055 Retail cost of revenues 477,012 75,155 — — 552,167 Less: Net asset optimization (expense) (5 ) (712 ) — — (717 ) Net, Gains (losses) on non-trading derivative instruments 5,784 (196 ) — — 5,588 Current period settlements on non-trading derivatives 16,302 206 — — 16,508 Retail gross margin $ 158,468 $ 66,041 $ — $ — $ 224,509 Total Assets $ 1,228,552 $ 421,896 $ 209,428 $ (1,353,927 ) $ 505,949 Goodwill $ 117,624 $ 2,530 $ — $ — $ 120,154 Year Ended December 31, 2016 Retail Retail Corporate Eliminations Spark Retail Total Revenues $ 417,229 $ 129,468 $ — $ — $ 546,697 Retail cost of revenues 286,795 58,149 — — 344,944 Less: Net asset optimization (expense) — (586 ) — — (586 ) Net, Gains on non-trading derivative instruments 17,187 5,067 — — 22,254 Current period settlements on non-trading derivatives (4,889 ) 2,605 — — (2,284 ) Retail gross margin $ 118,136 $ 64,233 $ — $ — $ 182,369 Total Assets $ 576,757 $ 242,739 $ 169,404 $ (613,670 ) $ 375,230 Goodwill $ 76,617 $ 2,530 $ — $ — $ 79,147 Year Ended December 31, 2015 Retail Retail Corporate Eliminations Spark Retail Total Revenues $ 229,490 $ 128,663 $ — $ — $ 358,153 Retail cost of revenues 170,684 70,504 — — 241,188 Less: Net asset optimization revenues — 1,494 — — 1,494 Net, (Losses) on non-trading derivative instruments (13,348 ) (5,075 ) — — (18,423 ) Current period settlements on non-trading derivatives 11,899 8,380 — — 20,279 Retail gross margin $ 60,255 $ 53,360 $ — $ — $ 113,615 Total Assets $ 150,245 $ 113,583 $ 88,823 $ (190,417 ) $ 162,234 Goodwill $ 16,476 $ 1,903 $ — $ — $ 18,379 Significant Customers For each of the years ended December 31, 2017 , 2016 and 2015 , the Company did not have any significant customers that individually accounted for more than 10% of the Company’s consolidated retail revenue. Significant Suppliers For the years ended December 31, 2017 , 2016 and 2015 , the Company had two , two and one significant suppliers, respectively, that individually accounted for more than 10% of the Company’s consolidated retail cost of revenues and net asset optimization.

Customer Acquisitions

Customer Acquisitions	12 Months Ended
	Dec. 31, 2017
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Customer Acquisitions	16. Customer Acquisitions On April 3, 2017, the Company and Spark HoldCo exercised an option to acquire approximately 44,000 RCEs from the original owner of Perigee. As of December 31, 2017 , the Company paid $7.5 million for customers transferred to date. The purchase price was capitalized as customer relationships and is being amortized over a three year period as customers begin using electricity under a contract with the Company. During the first quarter of 2015, the Company entered into a purchase and sale agreement for the purchase of approximately 9,500 RCEs in Northern California for a purchase price of $2.0 million . The transaction closed in April 2015. The purchase price was capitalized as customer relationships in our consolidated balance sheet and is being amortized over a three -year period as customers use natural gas under a contract with the Company.

Equity Method Investment

Equity Method Investment	12 Months Ended
	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investment	17. Equity Method Investment Investment in eREX Spark Marketing Co., Ltd In September 2015, the Company and Spark HoldCo, together with eREX Co., Ltd., a Japanese company, entered into an agreement ("eREX JV Agreement") to form a new joint venture, eREX Spark Marketing Co., Ltd ("eREX Spark"). As part of this agreement, the Company made contributions of 156.4 million Japanese Yen, or $1.4 million , for a 20% ownership interest in eREX Spark. The Company is entitled to share in 30% of the dividends distributed by eREX Spark for the first year a qualifying dividend is paid and for the subsequent four years thereafter. After this period, dividends will be distributed proportionately with the equity ownership of eREX Spark. eREX Spark's board of directors consists of four directors, one of whom is appointed by the Company. Based on the Company's significant influence, as reflected by the 20% equity ownership and 25% control of the eREX Spark board of directors, we recorded the investment in eREX Spark as an equity method investment. Our investment in eREX Spark was $2.5 million as of December 31, 2017 , reflecting contributions made by the Company through December 31, 2017 and our proportionate share of earnings as determined under the HLBV method as of December 31, 2017 , and recorded in other assets in the consolidated balance sheet. There were no basis differences between our initial contribution and the underlying net assets of eREX Spark. We recorded our proportionate share of eREX Spark's earnings of $0.2 million in our consolidated statement of operations for the year ended December 31, 2017 .

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	18. Subsequent Events Buyout of Verde Earnout Obligations On January 12, 2018 , we entered into an Agreement to Terminate Earnout Payments (the “Earnout Termination Agreement”) that terminated our obligation to make any required earnout payments under the agreement for our acquisition of the Verde Companies in exchange for CenStar’s issuance to Verde Energy of a promissory note in the principal amount of $5.9 million (the “Verde Earnout Termination Note”). See further discussion in Note 8 "Debt." In addition, the Earnout Termination Agreement provided for CenStar’s issuance to Verde Energy USA Holdings, LLC of an amended and restated promissory note (the “Amended and Restated Verde Promissory Note”), which amended and restated the Verde Promissory Note. See further discussion in Note 8 "Debt." Declaration of Dividends On January 18, 2018 , the Company declared a dividend of $0.18125 per share to holders of record of our Class A common stock on March 2, 2018 and payable on March 16, 2018 . On January 18, 2018, the Company declared a quarterly cash dividend in the amount of $0.546875 per share of Series A Preferred Stock. This amount represents an annualized dividend of $2.1875 per share. The dividend will be paid on April 16, 2018 to holders of record on April 2, 2018 of the Series A Preferred Stock. The Company anticipates Series A Preferred Stock dividends declared of $8.1 million in the aggregate for the year ended December 31, 2018 based on the Series A Preferred Stock outstanding as of the date these financial statements are issued. Expansion of Credit Facility On January 11, 2018 and January 23, 2018, we exercised the accordion feature in the Senior Credit Facility, which when combined with prior exercises, increased the total commitments under the Senior Credit Facility from $150.0 million to $200.0 million . Please see Note 8 "Debt" and “—Liquidity and Capital Resources—Senior Credit Facility.” Series A Preferred Stock Offering On January 26, 2018 , we issued 2,000,000 shares of Series A Preferred Stock and received net proceeds from the offering of approximately $48.9 million (net of underwriting discounts, commissions and a structuring fee). See Note 5 "Preferred Stock" for further discussion. Acquisition of HIKO On March 1, 2018, we entered into a Membership Interest Purchase Agreement pursuant to which we acquired all of the issued and outstanding membership interests of HIKO Energy, LLC, a New York limited liability company, for a total purchase price of $6.0 million in cash, plus working capital. HIKO Energy, LLC ("HIKO") has a total of approximately 29,000 RCEs located in 42 markets in 7 states. Initial accounting for the HIKO business combination is incomplete as of the date these financial statements are issued. Please see "Item 9B—Other Information—Acquisition of HIKO" for a more detailed description. Acquisition of Customers from NG&E On March 7, 2018, we entered into an asset purchase agreement with NG&E pursuant to which we will acquire approximately 50,000 RCEs from NG&E for a cash purchase price of $250 for each RCE, or approximately $12.5 million in the aggregate. These customers are expected to begin transferring after April 1, 2018 and are located in 24 markets in 8 states. Please see “Item 9B—Other Information—Acquisition of Customers from NG&E” for a more detailed description. Termination of Master Service Agreement On March 7, 2018, we, Retailco Services and NuDevco Retail mutually agreed to terminate the Master Services Agreement, effective April 1, 2018. We believe that Retailco Services was able to recognize cost savings and stabilize operating costs related to the operational support services in 2016 and 2017. Under the terms of the termination agreement, the operational support services will be transferred back to the Company, which may allow us to extract further savings by eliminating overhead attributable to managing and accounting for Retailco Services as a stand-alone business. Please see “Item 9B—Other Information—Termination of Master Service Agreement” for a more detailed description.

Basis of Presentation and Sum26

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	The accompanying consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). The Company's consolidated financial statements are presented on a consolidated basis and include all wholly-owned and controlled subsidiaries. We account for investments over which we have significant influence but not a controlling financial interest using the equity method of accounting. All significant intercompany transactions and balances have been eliminated in the consolidated financial statements.
Transactions with Affiliates	Transactions with Affiliates The Company enters into transactions with and pays certain costs on behalf of affiliates that are commonly controlled by W. Keith Maxwell III, and these affiliates enter into transactions with and pay certain costs on our behalf, in order to reduce risk, reduce administrative expense, create economies of scale, create strategic alliances and supply goods and services among these related parties. These transactions include, but are not limited to, certain services to the affiliated companies associated with employee benefits provided through the Company’s benefit plans, insurance plans, leased office space, administrative salaries for management due diligence work, recurring management consulting, and accounting, tax, legal, or technology services based on services provided, departmental usage, or headcount, which are considered reasonable by management. As such, the accompanying consolidated financial statements include costs that have been incurred by the Company and then directly billed or allocated to affiliates, and costs that have been incurred by our affiliates and then directly billed or allocated to us, and are recorded net in general and administrative expense on the consolidated statements of operations with a corresponding accounts receivable—affiliates or accounts payable—affiliates, respectively, recorded in the consolidated balance sheets. Additionally, the Company enters into transactions with certain affiliates for sales or purchases of natural gas and electricity, which are recorded in retail revenues, retail cost of revenues, and net asset optimization revenues in the consolidated statements of operations with a corresponding accounts receivable—affiliate or accounts payable—affiliate in the consolidated balance sheets. The allocations and related estimates and assumptions are described more fully in Note 14 "Transactions with Affiliates."
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of all unrestricted demand deposits and funds invested in highly liquid instruments with original maturities of three months or less. The Company periodically assesses the financial condition of the institutions where these funds are held and believes that its credit risk is minimal with respect to these institutions.
Accounts Receivable	Accounts Receivable Trade accounts receivable are recorded at the invoiced amount and do not bear interest. Accounts receivable in the consolidated balance sheets are net of allowance for doubtful accounts of $4.0 million and $2.3 million as of December 31, 2017 and 2016 , respectively. The Company accrues an allowance for doubtful accounts based upon estimated uncollectible accounts receivable considering historical collections, accounts receivable aging analysis, credit risk and other factors. The Company writes off accounts receivable balances against the allowance for doubtful accounts when the accounts receivable is deemed to be uncollectible. Bad debt expense of $6.6 million , $1.3 million and $7.9 million was recorded in general and administrative expense in the consolidated statements of operations for the years ended December 31, 2017 , 2016 and 2015 , respectively. The Company conducts business in many utility service markets where the local regulated utility purchases our receivables, and then becomes responsible for billing the customer and collecting payment from the customer (“POR programs”). This POR service results in substantially all of the Company’s credit risk being linked to the applicable utility, which generally has an investment-grade rating, and not to the end-use customer. The Company monitors the financial condition of each utility and currently believes that its susceptibility to an individually significant write-off as a result of concentrations of customer accounts receivable with those utilities is remote. Trade accounts receivable that are part of a local regulated utility’s POR program are recorded on a gross basis in accounts receivable in the consolidated balance sheets. The discount paid to the local regulated utilities is recorded in general and administrative expense in the consolidated statements of operations. In markets that do not offer POR services or when the Company chooses to directly bill its customers, certain receivables are billed and collected by the Company. The Company bears the credit risk on these accounts and records an appropriate allowance for doubtful accounts to reflect any losses due to non-payment by customers. The Company’s customers are individually insignificant and geographically dispersed in these markets. The Company writes off customer balances when it believes that amounts are no longer collectible and when it has exhausted all means to collect these receivables.
Inventory	Inventory Inventory consists of natural gas used to fulfill and manage seasonality for fixed and variable-price retail customer load requirements and is valued at the lower of weighted average cost or market. Purchased natural gas costs are recognized in the consolidated statements of operations, within retail cost of revenues, when the natural gas is sold and delivered out of the storage facility. There were no inventory impairments recorded for the years ended December 31, 2017 , 2016 and 2015 . When natural gas is sold costs are recognized in the consolidated statements of operations, within retail cost of revenues, at the weighted average cost value at the time of the sale.
Customer Acquisition Costs	Customer Acquisition Costs The Company has retail natural gas and electricity customer acquisition costs, net of $22.1 million and $18.8 million recorded in current assets and $6.9 million and $6.1 million recorded in noncurrent assets representing direct response advertising costs as of December 31, 2017 and 2016 , respectively. Customer acquisition costs are spending for organic customer acquisitions and do not include customer acquisitions through merger and acquisition activities, which are recorded as customer relationships. Amortization of customer acquisition costs, recorded in depreciation and amortization in the consolidated statements of operations, was $21.4 million , $17.5 million and $18.0 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Capitalized direct response advertising costs consist primarily of hourly and commission based telemarketing costs, door-to-door agent commissions and other direct advertising costs associated with proven customer generation, and are capitalized and amortized over the estimated two -year average life of a customer in accordance with the provisions of FASB ASC 340-20, Capitalized Advertising Costs . Recoverability of customer acquisition costs is evaluated based on a comparison of the carrying amount of the customer acquisition costs to the future net cash flows expected to be generated by the customers acquired, considering specific assumptions for customer attrition, per unit gross profit, and operating costs. These assumptions are based on forecasts and historical experience.
Customer Relationships, Non-compete Agreements, and Trademarks	Non-compete agreements The non-compete agreements provide the Company with a certain level of assurance that acquired companies' expected earnings streams will not be disrupted by competition from the companies’ previous members. The fair values of non-compete agreements are determined using the differential valuation approach at acquisition date. Under this approach, the Company estimates the present value of expected future cash flows under two scenarios; one scenario assumes the non-compete agreements are in place and the other scenario assumes the absence of non-compete agreements. The resulting difference between the two scenarios is the implied value of the non-compete agreements, which is further adjusted by an estimated probability factor representing the likelihood that previous members of acquired companies would be successful competitors. As a result of the Provider Companies and Major Energy Companies acquisitions, the Company recorded $1.2 million , net of amortization, as Acquired customer intangibles - current and $1.4 million , net of amortization, as Acquired customer intangibles - non-current as of December 31, 2016 related to these non-compete agreements. These non-compete agreements are amortized over their estimated three -year life on a straight-line basis. Customer Relationships Customer acquisitions through direct acquisitions of customer contracts or recorded as part of the acquisition method in accordance with FASB ASC Topic 805, Business Combinations ("ASC 805") are recorded as customer relationships and represent customer contract acquisitions not acquired through the direct response advertising discussed above at “ Customer Acquisition Costs. ” The Company has recorded $18.7 million and $12.1 million , net of amortization, as current assets as of December 31, 2017 and 2016 , respectively, and $34.8 million and $21.4 million , net of amortization, as non-current assets as of December 31, 2017 and 2016 , respectively, related to these intangible assets. These intangibles are amortized on a straight-line basis over the estimated average life of the related customer contracts acquired, which ranges from three years to six years . The acquired customer relationships intangibles related to Oasis, CenStar, Provider Companies, Major Energy Companies, Perigee Energy LLC, and Verde Companies are reflective of the acquired companies’ customer base, and were valued at the respective dates of acquisition using an excess earnings method under the income approach. Using this method, the Company estimated the future cash flows resulting from the existing customer relationships, considering attrition as well as charges for contributory assets, such as net working capital, fixed assets, and assembled workforce. These future cash flows were then discounted using an appropriate risk-adjusted rate of return by retail unit to arrive at the present value of the expected future cash flows. CenStar, Oasis and Perigee customer relationships are amortized to depreciation and amortization based on the expected future net cash flows by year. The acquired customer relationship intangibles related to the Major Energy Companies, the Provider Companies and the Verde Companies were bifurcated between hedged and unhedged and amortized to depreciation and amortization based on the expected future cash flows by year and expensed to retail cost of revenue based on the expected term of the underlying fixed price contract in each reporting period, respectively. Amortization expense was $17.8 million , $28.6 million , and $5.7 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Approximately $0.3 million , $15.8 million , and zero of the $17.8 million , $28.6 million , and $5.7 million customer relationships amortization expense for the twelve months ending December 31, 2017 , 2016 , and 2015 , respectively, was included in retail cost of revenue. We review customer relationships for impairment whenever events or changes in business circumstances indicate the carrying value of the intangible assets may not be recoverable. Impairment is indicated when the undiscounted cash flows estimated to be generated by the intangible assets are less than their respective carrying value. If an impairment exists, a loss would be recognized for the difference between the fair value and carrying value of the intangible assets. Trademarks Trademarks recorded as part of the acquisition method in accordance with ASC 805 represent the value associated with the recognition and positive reputation of an acquired company to its target markets. This value would otherwise have to be internally developed through significant time and expense or by paying a third party for its use. The fair values of trademark assets were determined at the date of acquisition using a royalty savings method under the income approach. Under this approach, the Company estimates the present value of expected cash flows resulting from avoiding royalty payments to use a third party trademark. The Company analyzes market royalty rates charged for licensing trademarks and applied an expected royalty rate to a forecast of estimated revenue, which was then discounted using an appropriate risk adjusted rate of return. The Company has recorded $8.6 million and $6.3 million , net of amortization, as other assets as of December 31, 2017 and 2016 related to these trademarks in other assets. These intangibles are amortized over the estimated five -year to twenty -year life of the trademarks on a straight-line basis. Amortization expense was $0.8 million , $0.4 million and $0.1 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. We review trademarks for impairment whenever events or changes in business circumstances indicate the carrying value of the intangible assets may not be recoverable. Impairment is indicated when the undiscounted cash flows estimated to be generated by the intangible assets are less than their respective carrying value. If an impairment exists, a loss would be recognized for the difference between the fair value and carrying value of the intangible assets.
Deferred Financing Costs	Deferred Financing Costs Costs incurred in connection with the issuance of long-term debt are capitalized and amortized to interest expense using the straight-line method over the life of the related long-term debt due to the variable nature of the Company’s long-term debt.
Property and Equipment	Property and Equipment The Company records property and equipment at historical cost. Depreciation expense is recorded on a straight-line method based on estimated useful lives. When assets are placed into service, management makes estimates with respect to useful lives and salvage values of the assets. When items of property and equipment are sold or otherwise disposed of, any gain or loss is recorded in the consolidated statements of operations.
Internal-Use Software	The Company capitalizes costs associated with internal-use software projects in accordance with FASB ASC Topic 350-40, Internal-Use Software . Capitalized costs are the costs incurred during the application development stage of the internal-use software project such as software configuration, coding, installation of hardware and testing. Costs incurred during the preliminary or post-implementation stage of the internal-use software project are expensed in the period incurred. These types of costs include formulation of ideas and alternatives, training and application maintenance. After internal-use software projects are completed, the associated capitalized costs are depreciated over the estimated useful life of the related asset. Interest costs incurred while developing internal-use software projects are capitalized in accordance with FASB ASC Topic 835-20, Capitalization of Interest .
Goodwill	Goodwill Goodwill represents the excess of cost over fair value of the assets of businesses acquired in accordance with FASB ASC Topic 350 Intangibles-Goodwill and Other ("ASC 350"). The goodwill on our consolidated balance sheet as of December 31, 2017 is associated with both our Retail Natural Gas and Retail Electricity reporting units. We determine our reporting units by identifying each unit that engaged in business activities from which it may earn revenues and incur expenses, had operating results regularly reviewed by the segment manager for purposes of resource allocation and performance assessment, and had discrete financial information. Goodwill is assessed for impairment whenever events or circumstances indicate that impairment of the carrying value of goodwill is likely, but no less often than annually as of October 31. On October 31, 2017, we elected to by-pass the option to perform a qualitative assessment of goodwill and performed a quantitative assessment of goodwill in accordance with guidance from ASC 350. This guidance permits an entity to first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform the two-step goodwill impairment test. If we fail the qualitative test or if we elect to by-pass the qualitative assessment, then we must compare our estimate of the fair value of a reporting unit with its carrying value, including goodwill. If the carrying value of the reporting unit exceeds its fair value, we perform the second step of the goodwill impairment test to measure the amount of goodwill impairment loss to be recorded, as necessary. The second step compares the implied fair value of the reporting unit’s goodwill to the carrying value, if any, of that goodwill. We determine the implied fair value of the goodwill in the same manner as determining the amount of goodwill to be recognized in a business combination. The inputs used in the determination of fair value are generally level 3 inputs.
Treasury Stock	Treasury Stock Treasury stock consists of Company's own stock that has been issued, but is subsequently reacquired by the Company. Treasury stock does not reduce the number of shares issued but does reduce the number of shares outstanding. These shares are not eligible to receive cash dividends. Accounting for treasury stock transactions is governed by FASB ASC Topic 550-30 Equity-Treasury Stock. We use the cost method to account for treasury shares. Purchases of shares of Class A common stock are recorded at cost, and the gross cost of the Class A common stock purchased is charged to a contra equity account entitled "Treasury Stock."
Equity Method Investment	Equity Method Investment The Company accounts for investments in unconsolidated entities using the equity method of accounting, as prescribed in FASB ASC Topic 323-10, Investments-Equity Method and Joint Venture, if the investment gives us the ability to exercise significant influence over, but not control, of an investee. Significant influence generally exists if we have an ownership interest representing between 20% and 50% of the voting stock of the investee. Under the equity method of accounting, investments are stated at initial cost and are adjusted for subsequent additional investments and our proportionate share of earnings or losses and distributions. Such investment is presented on the consolidated balance sheet under "Other assets" and our share of their income as "Interest and other income" on the consolidated statements of operations. The Company determines its equity investment earnings using the Hypothetical Liquidation at Book Value (HLBV) method. Under the HLBV method, a calculation is prepared at each balance sheet date to determine the amount the Company would receive if the investee were to liquidate all of its assets, as valued in accordance with U.S. GAAP, and distribute that cash to the investors. The difference between the calculated liquidation distribution amounts at the beginning and the end of the reporting period, after adjusting for capital contributions and distributions, is the Company's share of the earnings or losses from the equity investment for the period.
Segment Reporting	Segment Reporting The FASB ASC Topic 280, Segment Reporting , established standards for entities to report information about the operating segments and geographic areas in which they operate. The Company operates two segments, retail natural gas and retail electricity, and all of its operations are located in the United States.
Revenues and Cost of Revenues	Revenues and Cost of Revenues The Company’s revenues are derived primarily from the sale of natural gas and electricity to retail customers. The Company also records revenue from sales of natural gas and electricity to wholesale counterparties, including affiliates. Revenues are recognized by the Company using the following criteria: (1) persuasive evidence of an exchange arrangement exists, (2) delivery has occurred or services have been rendered, (3) the buyer’s price is fixed or determinable and (4) collection is reasonably assured. Utilizing these criteria, revenue is recognized when the natural gas or electricity is delivered. Similarly, cost of revenues is recognized when the commodity is delivered. Revenues for natural gas and electricity sales are recognized upon delivery under the accrual method. Natural gas and electricity sales that have been delivered but not billed by period end are estimated. Accrued unbilled revenues are based on estimates of customer usage since the date of the last meter read provided by the utility. Volume estimates are based on forecasted volumes and estimated customer usage by class. Unbilled revenues are calculated by multiplying these volume estimates by the applicable rate by customer class. Estimated amounts are adjusted when actual usage is known and billed. The Company records gross receipts taxes on a gross basis in retail revenues and retail cost of revenues. During the years ended December 31, 2017 , 2016 and 2015 , the Company’s retail revenues and retail cost of revenues included gross receipts taxes of $9.0 million , $5.3 million and $3.0 million , respectively. Costs for natural gas and electricity sales are recognized as the commodity is delivered to the customer under the accrual method. Natural gas and electricity costs that have not been billed to the Company by suppliers but have been incurred by period end are estimated. The Company estimates volumes for natural gas and electricity delivered based on the forecasted revenue volumes, estimated transportation cost volumes and estimation of other costs associated with retail load that varies by commodity utility territory. These costs include items like ISO fees, ancillary services and renewable energy credits. Estimated amounts are adjusted when actual usage is known and billed. The Company’s asset optimization activities, which primarily include natural gas physical arbitrage and other short term storage and transportation opportunities, meet the definition of trading activities and are recorded on a net basis in the consolidated statements of operations in net asset optimization revenues pursuant to FASB ASC Topic 815, Derivatives and Hedging .
Natural Gas Imbalances	Natural Gas Imbalances The consolidated balance sheets include natural gas imbalance receivables and payables, which primarily results when customers consume more or less gas than has been delivered by the Company to local distribution companies (“LDCs”). The settlement of natural gas imbalances varies by LDC, but typically the natural gas imbalances are settled in cash or in kind on a monthly, quarterly, semi-annual or annual basis. The imbalances are valued at an estimated net realizable value.
Fair Value	Fair Value FASB ASC Topic 820, Fair Value Measurement , established a single authoritative definition of fair value, set out a framework for measuring fair value, and requires disclosures about fair value measurements. The standard clarifies that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. The standard utilizes a fair value hierarchy that prioritizes the inputs to the valuation techniques used to measure fair value into three broad levels based on quoted prices in active market, observable market prices, and unobservable market prices. When the Company is required to measure fair value, and there is not a quoted or observable market price for a similar asset or liability, the Company utilizes the cost, income, or market valuation approach depending on the quality of information available to support management’s assumptions.
Derivative Instruments	Derivative Instruments The Company uses derivative instruments such as futures, swaps, forwards and options to manage the commodity price risks of its business operations. All derivatives, other than those for which an exception applies, are recorded in the consolidated balance sheets at fair value. Derivative instruments representing unrealized gains are reported as derivative assets while derivative instruments representing unrealized losses are reported as derivative liabilities. The Company has elected to offset amounts in the consolidated balance sheets for derivative instruments executed with the same counterparty under a master netting arrangement. One of the exceptions to fair value accounting, normal purchases and normal sales, has been elected by the Company for certain derivative instruments when the contract satisfies certain criteria, including a requirement that physical delivery of the underlying commodity is probable and is expected to be used in normal course of business. Retail revenues and retail cost of revenues resulting from deliveries of commodities under normal purchase contracts and normal sales contracts are included in earnings at the time of contract settlement. To manage commodity price risk, the Company holds certain derivative instruments that are not held for trading purposes and are not designated as hedges for accounting purposes. However, to the extent the Company does not hold offsetting positions for such derivatives, they believe these instruments represent economic hedges that mitigate their exposure to fluctuations in commodity prices. As part of the Company’s strategy to optimize its assets and manage related commodity risks, it also manages a portfolio of commodity derivative instruments held for trading purposes. The Company uses established policies and procedures to manage the risks associated with price fluctuations in these energy commodities and uses derivative instruments to reduce risk by generally creating offsetting market positions. Changes in the fair value of and amounts realized upon settlement of derivative instruments not held for trading purposes are recognized currently in retail costs of revenues. Changes in the fair value of and amounts realized upon settlement of derivative instruments held for trading purposes are recognized currently in earnings in net asset optimization revenues.
Income Taxes	Income Taxes The Company recognizes the amount of taxes payable or refundable for the year. In addition, the Company follows the asset and liability method of accounting for income taxes where deferred tax assets and liabilities are recognized for the expected future tax consequences of events that have been recognized in the financial statements or tax returns and operating loss carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in those years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in the tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is provided for deferred tax assets if it is more likely than not that these items will not be realized. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the projected future taxable income and tax planning strategies in making this assessment. Based upon the level of historical taxable income and projections for future taxable income over the periods in which the deferred tax assets are deductible, management believes it is more likely than not that we will realize the benefits of these deductible differences. The Company recognizes interest and penalties related to unrecognized tax benefits within the provision for income taxes on continuing operations in our consolidated statements of operations.
Earnings per Share	Earnings per Share Basic earnings per share (“EPS”) is computed by dividing net income attributable to shareholders (the numerator) by the weighted-average number of Class A common shares outstanding for the period (the denominator). Class B common shares are not included in the calculation of basic earnings per share because they are not participating securities and have no economic interest in the Company. Diluted earnings per share is similarly calculated except that the denominator is increased (1) using the treasury stock method to determine the potential dilutive effect of the Company’s outstanding unvested restricted stock units, (2) using the if-converted method to determine the potential dilutive effect of the Company’s Class B common stock and (3) using the if-converted method to determine the potential dilutive effect of the outstanding convertible subordinated notes into the Company's Class B common stock.
Non-controlling Interest	Non-controlling Interest The Company and NuDevco Retail and Retailco owned the following economic interests in Spark HoldCo at December 31, 2016 and December 31, 2017 , respectively. The Company NuDevco Retail and Retailco (1) (2) On December 31, 2016 38.85% 61.15% On December 31, 2017 38.12% 61.88% (1) In January 2016, Retailco succeeded to the interest of NuDevco Retail Holdings of its Class B common stock and an equal number of Spark HoldCo units it held pursuant to a series of transfers. (2) In January 2017, Retailco converted the CenStar Note and Oasis Note to 269,462 and 766,180 shares, respectively, of Class B common stock. See Note 4 "Equity" for further detail. Net income attributable to non-controlling interest for the years ended December 31, 2017 and 2016 represents NuDevco’s interest in Spark HoldCo. Income and expenses specifically attributable to the non-controlling interest and the Company are allocated accordingly (for example income tax expense (benefit), gain related to the remeasurement of the TRA liability as a result of U.S. Tax Reform, and income (loss) related to recast financial statements). The weighted average ownership percentages for the applicable reporting period are used to allocate the remaining income (loss) before income taxes to the each economic interest owner
Commitments and Contingencies	Commitments and Contingencies The Company enters into various firm purchase and sale commitments for natural gas, storage, transportation, and electricity that do not meet the definition of a derivative instrument. Management does not anticipate that such commitments will result in any significant gains or losses based on current market conditions. Liabilities for loss contingencies arising from claims, assessments, litigation, fines, penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. Legal costs incurred in connection with loss contingencies are expensed as incurred.
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of the Company’s consolidated financial statements requires estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the period. Actual results could materially differ from those estimates. Significant items subject to such estimates by the Company’s management include estimates for unbilled revenues and related cost of revenues, provisions for uncollectible receivables, valuation of customer acquisition costs, estimated useful lives of property and equipment, valuation of derivatives and reserves for contingencies.
Subsequent Events	Subsequent Events Subsequent events have been evaluated through the date these financial statements are issued. Any material subsequent events that occurred prior to such date have been properly recognized or disclosed in the consolidated financial statements.
Reclassifications	Reclassifications Certain amounts in the prior period financial statements have been reclassified to conform to the current period presentation. These reclassifications had no effect on reported earnings.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted Standards In March 2016, the FASB issued ASU No. 2016-09, Compensation - Stock Compensation (Topic 718) ("ASU 2016-09"). ASU 2016-09 includes provisions intended to simplify various aspects of accounting for shared-based payments, including income tax consequences, classification of awards as either equity or liability and classification on the statement of cash flows. This guidance is effective for annual and interim reporting periods of public entities beginning after December 15, 2016. The Company adopted ASU 2016-09 on January 1, 2017. The new standard requires prospective recognition of excess tax benefits resulting from stock-based compensation vesting and exercises to be recognized as a reduction of income taxes and reflected in operating cash flows. Previously, these amounts were recognized in additional paid-in capital and presented as a financing activity on the statement of cash flows. Net excess tax benefits of $0.2 million were recognized as a reduction of income taxes for the year ended December 31, 2017 . Prior periods have not been adjusted. The Company has elected to continue to estimate the number of stock-based awards expected to vest, as permitted by ASU 2016-09, rather than electing to account for forfeitures as they occur. ASU 2016-09 requires that employee taxes paid when an employer withholds shares for tax-withholding purposes to be reported as financing activities in the statement of cash flows. Previously, these cash flows were included in operating activities. The Company has elected to adopt this prospectively, as permitted by ASU 2016-09. This change resulted in a $1.1 million impact on the statement of cash flow for the year ended December 31, 2017 . In October 2016, the FASB issued ASU No. 2016-17, Consolidation (Topic 810): Interests Held through Related Parties that Are under Common Control ("ASU 2016-17"). ASU 2016-17 amends the consolidation guidance on how a reporting entity that is the single decision maker of a variable interest entity ("VIE") should treat indirect interests in the entity held through related parties that are under common control with the reporting entity when determining whether it is the primary beneficiary of that VIE. Under ASU 2016-17, a single decision maker of a VIE is required to consider indirect economic interests in the entity held through related parties on a proportionate basis when determining whether it is the primary beneficiary of that VIE. If a single decision maker and its related party are under common control, the single decision maker is required to consider indirect interests in the entity held through those related parties to be the equivalent of direct interests in their entirety. The amendments are effective for public business entities for fiscal years beginning after December 15, 2016 (the Company's first quarter of fiscal 2017), including interim periods within those fiscal years. The standard is to be applied retrospectively or through a cumulative effect adjustment to retained earnings as of the beginning of the fiscal year of adoption. The Company adopted ASU 2016-17 effective January 1, 2017, and the adoption had no impact on the Company's consolidated financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash ("ASU 2016-18"). ASU 2016-18 is intended to add and clarify guidance on the classification and presentation of restricted cash on the statement of cash flows. ASU 2016-18 requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The amendments are effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company adopted ASU 2016-18 effective April 1, 2017, and has included restricted cash with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. Standards adopted in 2018 In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The standard permits the use of either the retrospective or cumulative effect transition method. In December 2016, the FASB further issued ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers , to increase stakeholders' awareness of the proposals and to expedite improvements to ASU 2014-09. The FASB issued additional amendments to ASU No. 2014-09, as amended by ASU No. 2015-14: • March 2016 - ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) ("ASU 2016-08"). ASU 2016-08 clarifies the implementation guidance on principal versus agent considerations. The guidance includes indicators to assist an entity in determining whether it controls a specified good or service before it is transferred to customers. • April 2016 - ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing ("ASU 2016-10"). ASU 2016-10 covers two specific topics: performance obligations and licensing. This amendment includes guidance on immaterial promised goods or services, shipping or handling activities, separately identifiable performance obligations, functional or symbolic intellectual property licenses, sales-based and usage-based royalties, license restrictions (time, use, geographical) and licensing renewals. • May 2016 - ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow Scope Improvements and Practical Expedients ("ASU 2016-12"). ASU 2016-12 clarifies certain core recognition principles including collectability, sales tax presentation, noncash consideration, contract modifications and completed contracts at transition and disclosures no longer required if the full retrospective transition method is adopted. • September 2017 - ASU No. 2017-13, Amendments to SEC Paragraphs Pursuant to the Staff Announcement at the July 20, 2017 EITF Meeting and Rescission of Prior SEC Staff Announcements and Observer Comments ("ASU 2017-13"). ASU 2017-13 provides additional implementation guidance related to ASC Topic 606 and is effective for annual reporting periods beginning after December 15, 2017. • November 2017 - ASU No. 2017-14, Amendments to SEC Paragraphs Pursuant to Staff Accounting Bulletin No. 116 and SEC Release No. 33-10403 ("ASU 2017-14"). ASU 2017-14 amends various paragraphs in ASC 605, Revenue Recognition ; and ASC 606, Revenue from Contracts With Customers , that contain SEC guidance. The amendments include superseding ASC 605-10-S25-1 (SAB Topic 13) as a result of SEC Staff Accounting Bulletin No. 116 and adding ASC 606-10-S25-1 as a result of SEC Release No. 33-10403. In 2017, we collaborated with an external professional services firm to analyze the impact of the standard on our contract portfolio by reviewing our current accounting policies and practices to identify potential differences that would result from applying the requirements of the new standard to our revenue contracts. In addition, we identified and implemented appropriate changes to our business processes, systems and controls to support recognition and disclosure under the new standard. The Company adopted the new standard effective January 1, 2018 utilizing the full retrospective approach. The adoption of the new standard will result in an immaterial impact to our total revenues and operating income for the years ended December 31, 2017 and 2016, since our contracts with customers identify the delivery of products and services that are individually distinct performance obligations and revenue is recognized when performance obligations are satisfied. As a result, receivable balances related to revenue, including amounts related to unbilled revenue, are reflected as accounts receivable in the consolidated balance sheets. No other revenue related contract assets or liabilities are recorded. The standard requires expanded disclosures regarding the qualitative and quantitative information of an entity's nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Note, the Company’s asset optimization activities meet the definition of trading activities per FASB ASC Topic 815, Derivatives and Hedging, and are therefore excluded from the scope of Revenue from Contracts with Customers (Topic 606) . In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230), Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"). ASU 2016-15 provides guidance on the presentation and classification of eight specific cash flow issues in the statement of cash flows. Those issues are cash payment for debt prepayment or debt extinguishment costs; settlement of zero-coupon debt instrument or other debt instrument with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing; contingent consideration payments made after a business combination; cash proceeds from the settlement of insurance claims, cash received from settlement of corporate-owned life insurance policies; distribution received from equity method investees; beneficial interest in securitization transactions; and classification of cash receipts and payments that have aspects of more than one class of cash flows. The guidance is effective for interim and annual reporting periods beginning after December 15, 2017. This ASU is to be applied using a retrospective transition method for each period presented. The Company adopted ASU 2016-15 effective January 1, 2018 and will classify contingent consideration payments made after a business combination as cash outflows for operating and financing activities on a retrospective basis. Because of the change in accounting guidance, we expect to reclassify acquisition related payments of approximately $1.8 million and $0.8 million from cash flows from investing activities to cash flows from operating activities for the years ended December 31, 2017 and December 31, 2016, respectively. We expect to reclassify acquisition related payments of approximately $18.4 million and $2.0 million from cash flows from investing activities to cash flows from financing activities for the years ended December 31, 2017 and December 31, 2016, respectively. In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). ASU 2016-16 requires immediate recognition of the current and deferred income tax consequences of intercompany asset transfers other than inventory. Current U.S. GAAP prohibits the recognition of current and deferred income taxes for an intra-entity asset transfer until the asset has been sold to an outside party. This guidance is effective for annual and interim reporting periods of public entities beginning after December 15, 2017. This ASU is to be applied using a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company adopted ASU 2016-16 effective January 1, 2018 and the adoption of this standard will not have an impact on the Company's consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business ("ASU 2017-01"). ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting, including acquisitions, disposals, goodwill, and consolidation. ASU 2017-01 is effective for annual periods beginning after December 15, 2017, including interim periods within those periods and is to be applied prospectively to transactions on or after the adoption date. The Company adopted ASU 2017-01 effective January 1, 2018, and the adoption will not have an impact on the Company's historical consolidated financial statements. In May 2017, the FASB issued ASU No. 2017-09, Compensation - Stock Compensation (Topic 718) ("ASU 2017-09"). ASU 2017-09 provides guidance on when changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. An entity should account for the effects of a modification unless all of the following are met: • The fair value of the modified award is the same as the fair value of the original award immediately before the original award is modified • The vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified • The classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. The amendments in ASU 2017-09 are effective for all entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. The amendments are to be applied prospectively to an award modified on or after the adoption date. The Company adopted ASU 2017-09 effective January 1, 2018, and the adoption will not have an impact on the Company's consolidated financial statements. Standards Being Evaluated/Standards Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) ("ASU 2016-02"). ASU 2016-02 amends the existing accounting standards for lease accounting by requiring entities to include substantially all leases on the balance sheet by requiring the recognition of right-of-use assets and lease liabilities for all leases. Entities may elect to not recognize leases with a maximum possible term of less than 12 months. For lessees, a lease is classified as finance or operating and the asset and liability are initially measured at the present value of the lease payments. For lessors, accounting for leases is largely unchanged from previous guidance. ASU 2016-02 also requires qualitative disclosures along with certain specific quantitative disclosures for both lessees and lessors. The amendments in this ASU are effective for fiscal years beginning after December 15, 2018, with early adoption permitted, and are effective for interim periods in the year of adoption. The ASU should be applied using a modified retrospective approach, which requires lessees and lessors to recognize and measure leases at the beginning of the earliest period presented. The Company is currently evaluating the impact of adopting this guidance on its consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"). ASU 2017-04 simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. Under the amendments in this update, an entity should perform its annual or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. However, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. ASU 2017-04 should be applied on a prospective basis and is effective for annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently evaluating the impact of adopting this guidance on its consolidated financial statements.

Basis of Presentation and Sum27

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Schedule of Ownership Interests Percentage	The Company and NuDevco Retail and Retailco owned the following economic interests in Spark HoldCo at December 31, 2016 and December 31, 2017 , respectively. The Company NuDevco Retail and Retailco (1) (2) On December 31, 2016 38.85% 61.15% On December 31, 2017 38.12% 61.88% (1) In January 2016, Retailco succeeded to the interest of NuDevco Retail Holdings of its Class B common stock and an equal number of Spark HoldCo units it held pursuant to a series of transfers. (2) In January 2017, Retailco converted the CenStar Note and Oasis Note to 269,462 and 766,180 shares, respectively, of Class B common stock. The Company and NuDevco Retail and Retailco owned the following economic interests in Spark HoldCo at December 31, 2016 and December 31, 2017 , respectively. Non-controlling Interest Economic Interest The Company NuDevco Retail and Retailco (1) (2) December 31, 2016 38.85 % 61.15 % December 31, 2017 38.12 % 61.88 % (1) In January 2016, Retailco succeeded to the interest of NuDevco Retail Holdings of its Class B common stock and an equal number of Spark HoldCo units it held pursuant to a series of transfers. (2) In January 2017, Retailco converted the CenStar Note and Oasis Note into 269,462 and 766,180 shares, respectively, of Class B common stock.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Allocation of the Purchase Consideration	NG&E acquired Perigee on February 3, 2017 and the fair value of the net assets acquired was as follows (in thousands): As of December 31, 2017 Cash $ 23 Intangible assets - customer relationships 1,100 Goodwill 1,540 Net working capital, net of cash acquired 2,085 Fair value of derivative liabilities (443 ) Total $ 4,305 The allocation of the purchase consideration is as follows (in thousands): Final as of December 31, 2016 Cash $ 431 Net working capital, net of cash acquired 812 Intangible assets - customer relationships and non-compete agreements 24,417 Intangible assets - trademark 529 Goodwill 26,040 Fair value of derivative liabilities (18,163 ) Total $ 34,066 NG&E acquired the Major Energy Companies on April 15, 2016 and the fair value of the net assets acquired was as follows (in thousands): Reported as of December 31, 2016 2017 Adjustments (1) December 31, 2017 Cash $ 17,368 $ — $ 17,368 Property and equipment 14 — 14 Intangible assets - customer relationships & non-compete agreements 24,271 — 24,271 Other assets - trademarks 4,973 — 4,973 Non-current deferred tax assets 1,042 — 1,042 Goodwill 34,728 260 34,988 Net working capital, net of cash acquired (6,746 ) — (6,746 ) Fair value of derivative liabilities (7,260 ) — (7,260 ) Total $ 68,390 $ 260 $ 68,650 (1) Changes to the purchase price allocation during 2017 related to NG&E's working capital settlement with the Major Energy Companies' sellers. The allocation of the purchase consideration is as follows (in thousands): December 31, 2017 Cash and restricted cash $ 1,653 Property and equipment 4,560 Intangible assets - customer relationships 28,700 Intangible assets - trademarks 3,000 Goodwill 39,207 Net working capital, net of cash acquired 19,132 Deferred tax liability (3,126 ) Fair value of derivative liabilities (1,942 ) Total $ 91,184
Unaudited Pro Forma Revenue and Earnings Summary	The following unaudited pro forma revenue and earnings summary presents consolidated information of the Company as if the acquisition had occurred on January 1, 2016 (in thousands): Year Ended December 31, 2017 2016 Revenues $ 868,415 $ 716,696 Earnings $ 18,047 $ 17,860 The following unaudited pro forma revenue and earnings summary presents consolidated information of the Company as if the acquisition had occurred on January 1, 2015 (in thousands): Year Ended December 31, 2016 2015 Revenue $603,673 $547,381 Earnings $15,776 $15,460 The following unaudited pro forma revenue and earnings summary presents consolidated information of the Company as if the acquisition had occurred on January 1, 2016 (in thousands): Year Ended December 31, 2017 2016 Revenues $ 868,415 $ 716,696 Earnings $ 18,047 $ 17,860

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Ownership Interests Percentage	The Company and NuDevco Retail and Retailco owned the following economic interests in Spark HoldCo at December 31, 2016 and December 31, 2017 , respectively. The Company NuDevco Retail and Retailco (1) (2) On December 31, 2016 38.85% 61.15% On December 31, 2017 38.12% 61.88% (1) In January 2016, Retailco succeeded to the interest of NuDevco Retail Holdings of its Class B common stock and an equal number of Spark HoldCo units it held pursuant to a series of transfers. (2) In January 2017, Retailco converted the CenStar Note and Oasis Note to 269,462 and 766,180 shares, respectively, of Class B common stock. The Company and NuDevco Retail and Retailco owned the following economic interests in Spark HoldCo at December 31, 2016 and December 31, 2017 , respectively. Non-controlling Interest Economic Interest The Company NuDevco Retail and Retailco (1) (2) December 31, 2016 38.85 % 61.15 % December 31, 2017 38.12 % 61.88 % (1) In January 2016, Retailco succeeded to the interest of NuDevco Retail Holdings of its Class B common stock and an equal number of Spark HoldCo units it held pursuant to a series of transfers. (2) In January 2017, Retailco converted the CenStar Note and Oasis Note into 269,462 and 766,180 shares, respectively, of Class B common stock.
Schedule of Net Income and Income Tax Expense (Benefit) Attributable to Non-Controlling Interest	The following table summarizes the portion of net income and income tax expense (benefit) attributable to non-controlling interest (in thousands): 2017 2016 2015 Net income allocated to non-controlling interest $ 56,696 $ 52,300 $ 21,779 Income tax expense (benefit) allocated to non-controlling interest (731 ) 1,071 (331 ) Net income attributable to non-controlling interest $ 57,427 $ 51,229 $ 22,110
Computation of Earnings Per Share	The following table presents the computation of earnings per share for the years ended December 31, 2017 and 2016 (in thousands, except per share data): Year Ended December 31, 2017 2016 2015 Net income attributable to Spark Energy, Inc. stockholders $ 18,854 $ 14,444 $ 3,865 Less: Dividend on Series A preferred stock 3,038 — — Net income attributable to stockholders of Class A common stock $ 15,816 $ 14,444 $ 3,865 Basic weighted average Class A common shares outstanding 13,143 11,402 6,129 Basic EPS attributable to stockholders $ 1.20 $ 1.27 $ 0.63 Net income attributable to stockholders of Class A common stock $ 15,816 $ 14,444 $ 3,865 Effect of conversion of Class B common stock to shares of Class A common stock — — — Effect of conversion of convertible subordinated notes into shares of Class B common stock and shares of Class B common stock into shares of Class A common stock (1) — (310 ) (334 ) Diluted net income attributable to stockholders of Class A common stock $ 15,816 $ 14,134 $ 3,531 Basic weighted average Class A common shares outstanding 13,143 11,402 6,129 Effect of dilutive Class B common stock — — — Effect of dilutive convertible subordinated notes into shares of Class B common stock and shares of Class B common stock into shares of Class A common stock — 1,010 420 Effect of dilutive restricted stock units 203 278 106 Diluted weighted average shares outstanding 13,346 12,690 6,655 Diluted EPS attributable to stockholders $ 1.19 $ 1.11 $ 0.53 (1) The CenStar Note and Oasis Note converted into 269,462 and 766,180 shares of Class B common stock on January 8, 2017, and January 31, 2017, respectively.
Schedule of Variable Interest Entities	The following table includes the carrying amounts and classification of the assets and liabilities of Spark HoldCo that are included in the Company's consolidated balance sheet as of December 31, 2017 (in thousands): December 31, 2017 Assets Current assets: Cash and cash equivalents $ 29,385 Accounts receivable 158,814 Other current assets 105,165 Total current assets 293,364 Non-current assets: Goodwill 120,154 Other assets 62,552 Total non-current assets 182,706 Total Assets $ 476,070 Liabilities Current liabilities: Accounts Payable and Accrued Liabilities $ 110,152 Current portion of Senior Credit Facility 7,500 Contingent consideration 4,024 Other current liabilities 8,933 Total current liabilities 130,609 Long-term liabilities: Long-term portion of Senior Credit Facility 117,750 Contingent consideration 626 Other long-term liabilities 663 Total long-term liabilities 119,039 Total Liabilities $ 249,648

Preferred Stock (Tables)

Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Summary of Mezzanine Equity	A summary of the Company's mezzanine equity for the year ended December 31, 2017 is as follows: (in thousands) Mezzanine equity at December 31, 2016 $ — Issuance of Series A Preferred Stock, net of issuance cost 40,241 Accumulated dividends on Series A Preferred Stock 932 Mezzanine equity at December 31, 2017 $ 41,173

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following amounts as of (in thousands): Estimated December 31, 2017 December 31, 2016 Information technology 2 – 5 $ 34,103 $ 29,675 Leasehold improvements 2 – 5 4,568 4,568 Furniture and fixtures 2 – 5 1,964 1,024 Building improvements 2 – 5 809 — Total 41,444 35,267 Accumulated depreciation (33,169 ) (30,561 ) Property and equipment—net $ 8,275 $ 4,706

Goodwill, Customer Relationsh32

Goodwill, Customer Relationships and Trademarks (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill and Intangible Assets	Goodwill, customer relationships and trademarks consist of the following amounts as of (in thousands): December 31, 2017 December 31, 2016 Goodwill $ 120,154 $ 79,147 Customer Relationships — Acquired (1) Cost $ 93,371 $ 63,571 Accumulated amortization (46,681 ) (31,660 ) Customer Relationships —Acquired, net $ 46,690 $ 31,911 Customer Relationships — Other (2) Cost $ 12,336 $ 4,320 Accumulated amortization (5,534 ) (2,708 ) Customer Relationships —Other, net $ 6,802 $ 1,612 Trademarks (3) Cost $ 9,770 $ 6,770 Accumulated amortization (1,212 ) (431 ) Trademarks, net $ 8,558 $ 6,339 (1) Customer relationships—Acquired represent those customer acquisitions accounted for under the acquisition method in accordance with ASC 805. See Note 3 "Acquisitions" for further discussion. (2) Customer relationships—Other represent portfolios of customer contracts not accounted for in accordance with ASC 805 as these acquisitions were not in conjunction with the acquisition of businesses. See Note 16 "Customer Acquisitions" for further discussion. (3) Trademarks reflect values associated with the recognition and positive reputation of acquired businesses accounted for as part of the acquisition method in accordance with ASC 805 through the acquisitions of CenStar, Oasis, the Provider Companies, the Major Energy Companies and the Verde Companies. These trademarks are recorded as other assets in the consolidated balance sheets. See Note 3 "Acquisitions" for further discussion. Changes in goodwill, customer relationships and trademarks consisted of the following (in thousands): Goodwill (1) Customer Relationships— Acquired & Non-Compete Agreements Customer Relationships — Other Trademarks Balance at December 31, 2014 $ — $ — $ 1,501 $ — Additions $ — $ — $ 2,731 $ — Acquisition of CenStar 6,396 5,494 — 651 Acquisition of Oasis 11,983 9,389 — 617 Amortization expense — (4,503 ) (1,183 ) (74 ) Balance at December 31, 2015 $ 18,379 $ 10,380 $ 3,049 $ 1,194 Additions $ — $ — $ — $ — Acquisition of Provider Companies 26,040 24,417 — 529 Acquisition of Major Energy Companies 34,728 24,271 — 4,973 Amortization expense — (27,157 ) (1,437 ) (357 ) Balance at December 31, 2016 $ 79,147 $ 31,911 $ 1,612 $ 6,339 Additions (Major Working Capital Adjustment) $ 260 $ — $ — $ — Acquisition of Perigee 1,540 1,100 — — Acquisition of Verde 39,207 28,700 — 3,000 Additions (Other) (2) — — 8,016 — Amortization expense — (15,021 ) (2,826 ) (781 ) Balance at December 31, 2017 $ 120,154 $ 46,690 $ 6,802 $ 8,558 (1) Changes in goodwill for the year ended December 31, 2017 include NG&E's working capital settlement with the Major Energy Companies' sellers of $0.3 million , Perigee's goodwill of $1.5 million , and the Verde Companies' goodwill of $39.2 million . (2) Includes $8.0 million related to customer contract purchases for the year ended December 31, 2017 .
Estimated Future Amortization Expense of Intangible Assets	Estimated future amortization expense for customer relationships and trademarks at December 31, 2017 is as follows (in thousands): Year Ending December 31, 2018 $ 19,469 2019 14,894 2020 10,474 2021 8,912 2022 4,700 > 5 years 3,601 Total $ 62,050

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Debt	Debt consists of the following amounts as of (in thousands): December 31, 2017 December 31, 2016 Current portion of Senior Credit Facility—Bridge Loan (5) $ 7,500 $ — Current portion of Prior Senior Credit Facility—Working Capital Line (1) — 29,000 Current portion of Prior Senior Credit Facility—Acquisition Line (2) — 22,287 Current portion of Note Payable—Pacific Summit Energy — 15,501 Convertible subordinated notes to affiliate (3) — 6,582 Current portion of Note Payable—Verde 13,443 — Total current debt 20,943 73,370 Long-term portion of Senior Credit Facility (4) (5) 117,750 — Subordinated Debt — 5,000 Long-term portion of Note Payable—Verde 7,051 — Total long-term debt 124,801 5,000 Total debt $ 145,744 $ 78,370 (1) As of December 31, 2016 , the Company had $29.6 million in letters of credit issued. (2) As of December 31, 2016 , the weighted average interest rate on the current portion of our Prior Senior Credit Facility was 4.93% . (3) On October 5, 2016, RAC issued to the Company an irrevocable commitment to convert the CenStar Note and the Oasis Note into shares of Class B common stock on January 8, 2017 and January 31, 2017, respectively. RAC assigned the CenStar Note and Oasis Note to Retailco on January 4, 2017, and on January 8, 2017 and January 31, 2017, the CenStar Note and Oasis Note were converted into 269,462 and 766,180 shares of Class B common stock, respectively. (4) As of December 31, 2017 , the Company had $47.2 million in letters of credit issued. (5) As of December 31, 2017 , the weighted average interest rate on our Senior Credit Facility was 4.61% .
Components of Interest Expense	Interest expense consists of the following components for the periods indicated (in thousands): Years Ended December 31, 2017 2016 2015 Interest incurred on Senior Credit Facility $ 3,275 $ 1,730 $ 1,144 Accretion related to Earnouts (1) 4,108 5,060 — Letters of credit fees and commitment fees 1,125 883 517 Amortization of deferred financing costs (2) 1,035 668 412 Interest incurred on convertible subordinated notes to affiliate (3) 1,052 518 207 Interest incurred on subordinated debt 167 — — Interest on Verde promissory note 372 — — Interest expense $ 11,134 $ 8,859 $ 2,280 (1) Includes accretion related to the Provider Earnout of $0.1 million , the Major Earnout of $3.8 million , and the Verde Earnout of $0.2 million for the year ended December 31, 2017 and accretion related to the Provider Earnout of $0.1 million and the Major Earnout of $4.9 million for the year ended December 31, 2016 . (2) Write offs of deferred financing costs included in the above amortization were $0.1 million in connection with the amended and restated Prior Senior Credit Facility on July 8, 2015, $0.3 million upon extinguishment of the Seventh Amended Credit Facility and $0.1 million in connection with the execution of the Seventh Amended Credit Facility for the year ended December 31, 2015 . (3) Includes amortization of the discount on the convertible subordinated notes to affiliates of zero , $0.2 million , and less than $0.1 million for the years ended December 31, 2017 , 2016 , and 2015 .

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables present assets and liabilities measured and recorded at fair value in the Company’s consolidated balance sheets on a recurring basis by and their level within the fair value hierarchy as of (in thousands): Level 1 Level 2 Level 3 Total December 31, 2017 Non-trading commodity derivative assets $ 158 $ 33,886 $ — $ 34,044 Trading commodity derivative assets — 456 — 456 Total commodity derivative assets $ 158 $ 34,342 $ — $ 34,500 Non-trading commodity derivative liabilities $ (387 ) $ (950 ) $ — $ (1,337 ) Trading commodity derivative liabilities (555 ) (237 ) — (792 ) Total commodity derivative liabilities $ (942 ) $ (1,187 ) $ — $ (2,129 ) Contingent payment arrangement $ — $ — $ (4,650 ) $ (4,650 ) Level 1 Level 2 Level 3 Total December 31, 2016 Non-trading commodity derivative assets $ 1,511 $ 9,385 $ — $ 10,896 Trading commodity derivative assets 101 430 — 531 Total commodity derivative assets $ 1,612 $ 9,815 $ — $ 11,427 Non-trading commodity derivative liabilities $ — $ (661 ) $ — $ (661 ) Trading commodity derivative liabilities — (87 ) — (87 ) Total commodity derivative liabilities $ — $ (748 ) $ — $ (748 ) Contingent payment arrangement $ — $ — $ (22,653 ) $ (22,653 )
Reconciliations of Liabilities Measured at Fair Value on a Recurring Basis (Level 3)	The following tables present reconciliations of liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the years ended December 31, 2017 and 2016 , respectively. CenStar Earnout Major Earnout and Stock Earnout Provider Earnout Verde Earnout Total Fair Value at December 31, 2015 $ 500 $ — $ — $ — $ 500 Purchase price contingent consideration $ — $ 13,910 $ 4,823 $ — 18,733 Change in fair value of contingent consideration, net 843 (1,140 ) — — (297 ) Accretion of contingent earnout consideration (included within interest expense) — 4,990 70 — 5,060 Payments and settlements (1) (1,343 ) — — — (1,343 ) Fair Value at December 31, 2016 $ — $ 17,760 $ 4,893 $ — $ 22,653 Purchase price consideration $ — $ — $ — $ 5,400 $ 5,400 Change in fair value of contingent consideration, net — (9,555 ) 500 347 (8,708 ) Accretion of contingent earnout consideration (included within interest expense) — 3,848 107 153 4,108 Payments and settlements (1) — (7,403 ) (5,500 ) (5,900 ) (18,803 ) Fair Value at December 31, 2017 $ — $ 4,650 $ — $ — $ 4,650 (1) Payments and settlements include pay downs at maturity and the termination of the Verde Earnout liability, which was replaced with the Verde Earnout Termination Note. See discussion above and in Note 8 "Debt."

Accounting for Derivative Ins35

Accounting for Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Volumetric Underlying Derivative Transactions	The following table summarizes the net notional volume buy/(sell) of the Company’s open derivative financial instruments accounted for at fair value, broken out by commodity, as of (in thousands): Non-trading Commodity Notional December 31, 2017 December 31, 2016 Natural Gas MMBtu 9,191 8,016 Natural Gas Basis MMBtu — — Electricity MWh 8,091 3,958 Trading Commodity Notional December 31, 2017 December 31, 2016 Natural Gas MMBtu 26 (953 ) Natural Gas Basis MMBtu (225 ) (380 )
Gains (Losses) on Derivative Instruments	Gains (losses) on derivative instruments, net and current period settlements on derivative instruments were as follows for the periods indicated (in thousands): Year Ended December 31, 2017 2016 2015 Gain (loss) on non-trading derivatives, net 5,588 22,254 (18,423 ) (Loss) gain on trading derivatives, net (580 ) 153 (74 ) Gain (loss) on derivatives, net $ 5,008 $ 22,407 $ (18,497 ) Current period settlements on non-trading derivatives (1) (2) (3) (4) 16,508 (2,284 ) 20,279 Current period settlements on trading derivatives (199 ) 138 268 Total current period settlements on derivatives (1) (2) (3) (4) $ 16,309 $ (2,146 ) $ 20,547 (1) Excludes settlements of less than $0.1 million , $1.0 million and $3.4 million , respectively, for the years ended December 31, 2017 , 2016 , and 2015 related to non-trading derivative liabilities assumed in the acquisitions of CenStar and Oasis. (2) Excludes settlements of $0.5 million and $25.6 million , respectively, for the years ended December 31, 2017 and 2016 related to non-trading derivative liabilities assumed in the acquisitions of Provider Companies and Major Energy Companies. (3) Excludes settlements of $1.1 million for the year ended December 31, 2017 related to non-trading derivative liabilities assumed in the acquisitions of Perigee and other customers. (4) Excludes settlements of $1.7 million for the year ended December 31, 2017 related to non-trading derivative liabilities assumed in the acquisition of the Verde Companies.
Offsetting Assets	The following tables summarize the fair value and offsetting amounts of the Company’s derivative instruments by counterparty and collateral received or paid as of (in thousands): December 31, 2017 Description Gross Assets Gross Net Assets Cash Net Amount Non-trading commodity derivatives $ 60,167 $ (29,432 ) $ 30,735 $ — $ 30,735 Trading commodity derivatives 918 (462 ) 456 — 456 Total Current Derivative Assets 61,085 (29,894 ) 31,191 — 31,191 Non-trading commodity derivatives 16,055 (12,746 ) 3,309 — 3,309 Trading commodity derivatives — — — — — Total Non-current Derivative Assets 16,055 (12,746 ) 3,309 — 3,309 Total Derivative Assets $ 77,140 $ (42,640 ) $ 34,500 $ — $ 34,500 December 31, 2016 Description Gross Assets Gross Net Assets Cash Net Amount Non-trading commodity derivatives $ 19,657 $ (11,844 ) $ 7,813 $ — $ 7,813 Trading commodity derivatives 614 (83 ) 531 — 531 Total Current Derivative Assets 20,271 (11,927 ) 8,344 — 8,344 Non-trading commodity derivatives 7,874 (4,791 ) 3,083 — 3,083 Total Non-current Derivative Assets 7,874 (4,791 ) 3,083 — 3,083 Total Derivative Assets $ 28,145 $ (16,718 ) $ 11,427 $ — $ 11,427
Offsetting Liabilities	December 31, 2017 Description Gross Gross Net Cash Net Amount Non-trading commodity derivatives $ (4,517 ) $ 3,059 $ (1,458 ) $ 65 $ (1,393 ) Trading commodity derivatives (517 ) 273 (244 ) — (244 ) Total Current Derivative Liabilities (5,034 ) 3,332 (1,702 ) 65 (1,637 ) Non-trading commodity derivatives (676 ) 732 56 56 Trading commodity derivatives (566 ) 18 (548 ) — (548 ) Total Non-current Derivative Liabilities (1,242 ) 750 (492 ) — (492 ) Total Derivative Liabilities $ (6,276 ) $ 4,082 $ (2,194 ) $ 65 $ (2,129 ) December 31, 2016 Description Gross Gross Net Cash Net Amount Non-trading commodity derivatives $ (662 ) $ 69 $ (593 ) $ (593 ) Trading commodity derivatives (92 ) 5 (87 ) — (87 ) Total Current Derivative Liabilities (754 ) 74 (680 ) — (680 ) Non-trading commodity derivatives (305 ) 237 (68 ) — (68 ) Total Non-current Derivative Liabilities (305 ) 237 (68 ) — (68 ) Total Derivative Liabilities $ (1,059 ) $ 311 $ (748 ) $ — $ (748 )

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	The following table summarizes equity classified restricted stock unit activity and unvested restricted stock units for the year ended December 31, 2017 : Number of Shares (in thousands) Weighted Average Grant Date Fair Value Unvested at December 31, 2016 526 $ 9.56 Granted 307 18.10 Dividend reinvestment issuances 27 15.64 Vested (180 ) 17.88 Forfeited (40 ) 13.27 Unvested at December 31, 2017 640 $ 11.56 The following table summarizes liability classified restricted stock unit activity and unvested restricted stock units for the year ended December 31, 2017 : Number of Shares (in thousands) Weighted Average Reporting Date Fair Value Unvested at December 31, 2016 252 $ 15.15 Granted 140 12.40 Dividend reinvestment issuances 10 12.40 Vested (176 ) 16.93 Forfeited (2 ) 12.40 Unvested at December 31, 2017 224 $ 12.40

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Provision (Benefit) for Income Taxes	The provision for income taxes included the following components: (in thousands) 2017 2016 2015 Current: Federal $ 6,992 $ 5,361 $ 268 State 1,952 1,683 (277 ) Total Current 8,944 7,044 (9 ) Deferred: Federal 26,583 2,944 1,820 State 2,001 438 163 Total Deferred 28,584 3,382 1,983 Provision for income taxes $ 37,528 $ 10,426 $ 1,974
Schedule of Reconciliation of Income Tax Benefit	The following table reconciles the income tax benefit included in the consolidated statement of operations with income tax expense that would result from application of the statutory federal tax rate, 35% for the years ended December 31, 2017 and 2016 , respectively, to loss before income tax expense (benefit): (in thousands) 2017 2016 Expected provision at federal statutory rate $ 39,833 $ 26,635 Increase (decrease) resulting from: Impact of U.S. Tax Reform 13,217 — Non-controlling interest (19,810 ) (17,740 ) State income taxes, net of federal income tax effect 2,569 1,346 Other 1,719 185 Provision for income taxes $ 37,528 $ 10,426
Schedule of Deferred Tax Assets	The components of the Company’s deferred tax assets as of December 31, 2017 and 2016 are as follows: (in thousands) 2017 2016 Deferred Tax Assets: Investment in Spark HoldCo $ 18,340 $ 35,359 Benefit of TRA Liability 8,175 19,705 Federal net operating loss carryforward 660 2,076 State net operating loss carryforward 166 366 Total deferred tax assets 27,341 57,506 Deferred Tax Liabilities: Derivative liabilities (811 ) (1,849 ) Intangibles (2,287 ) (1,519 ) Property and equipment — (10 ) Other (58 ) (19 ) Total deferred tax liabilities (3,156 ) (3,397 ) Total deferred tax assets/liabilities $ 24,185 $ 54,109

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Reconciliation of Retail Gross Margin to Income Before Income Tax Expense	Below is a reconciliation of retail gross margin to income before income tax expense (in thousands): Years Ended December 31, (in thousands) 2017 2016 2015 Reconciliation of Retail Gross Margin to Income before taxes Income before income tax expense $ 113,809 $ 76,099 $ 27,949 Change in Tax Receivable Agreement Liability (22,267 ) — — Interest and other income (256 ) (957 ) (324 ) Interest expense 11,134 8,859 2,280 Operating Income 102,420 84,001 29,905 Depreciation and amortization 42,341 32,788 25,378 General and administrative 101,127 84,964 61,682 Less: Net asset optimization (expenses) revenue (717 ) (586 ) 1,494 Net, Gain (losses) on non-trading derivative instruments 5,588 22,254 (18,423 ) Net, Cash settlements on non-trading derivative instruments 16,508 (2,284 ) 20,279 Retail Gross Margin $ 224,509 $ 182,369 $ 113,615
Schedule of Financial Data for Business Segments	Financial data for business segments are as follows (in thousands): Year Ended December 31, 2017 Retail Retail Corporate Eliminations Spark Retail Total Revenues $ 657,561 $ 140,494 $ — $ — $ 798,055 Retail cost of revenues 477,012 75,155 — — 552,167 Less: Net asset optimization (expense) (5 ) (712 ) — — (717 ) Net, Gains (losses) on non-trading derivative instruments 5,784 (196 ) — — 5,588 Current period settlements on non-trading derivatives 16,302 206 — — 16,508 Retail gross margin $ 158,468 $ 66,041 $ — $ — $ 224,509 Total Assets $ 1,228,552 $ 421,896 $ 209,428 $ (1,353,927 ) $ 505,949 Goodwill $ 117,624 $ 2,530 $ — $ — $ 120,154 Year Ended December 31, 2016 Retail Retail Corporate Eliminations Spark Retail Total Revenues $ 417,229 $ 129,468 $ — $ — $ 546,697 Retail cost of revenues 286,795 58,149 — — 344,944 Less: Net asset optimization (expense) — (586 ) — — (586 ) Net, Gains on non-trading derivative instruments 17,187 5,067 — — 22,254 Current period settlements on non-trading derivatives (4,889 ) 2,605 — — (2,284 ) Retail gross margin $ 118,136 $ 64,233 $ — $ — $ 182,369 Total Assets $ 576,757 $ 242,739 $ 169,404 $ (613,670 ) $ 375,230 Goodwill $ 76,617 $ 2,530 $ — $ — $ 79,147 Year Ended December 31, 2015 Retail Retail Corporate Eliminations Spark Retail Total Revenues $ 229,490 $ 128,663 $ — $ — $ 358,153 Retail cost of revenues 170,684 70,504 — — 241,188 Less: Net asset optimization revenues — 1,494 — — 1,494 Net, (Losses) on non-trading derivative instruments (13,348 ) (5,075 ) — — (18,423 ) Current period settlements on non-trading derivatives 11,899 8,380 — — 20,279 Retail gross margin $ 60,255 $ 53,360 $ — $ — $ 113,615 Total Assets $ 150,245 $ 113,583 $ 88,823 $ (190,417 ) $ 162,234 Goodwill $ 16,476 $ 1,903 $ — $ — $ 18,379

Formation and Organization (Det

Formation and Organization (Details)	Jul. 31, 2015USD ($)	Jul. 08, 2015USD ($)	Dec. 31, 2017USD ($)vote$ / shares	Dec. 31, 2016USD ($)$ / shares
Class of Stock [Line Items]
Tax receivable agreement, percent of net cash savings			85.00%
Tax receivable agreement, deferral period			5 years
Tax receivable agreement, deferral period taken			1 year
Tax receivable agreement payment | $			$ 4,622,000	$ 3,775,000
Common Class B
Class of Stock [Line Items]
Common stock, par value per share (in dollars per share) | $ / shares			$ 0.01	$ 0.01
Common stock voting rights ratio | vote			1
Common Class A
Class of Stock [Line Items]
Common stock, par value per share (in dollars per share) | $ / shares			$ 0.01	$ 0.01
Common stock voting rights ratio | vote			1
Common stock, exchange ratio			1
Retailco and NuDevco Retail
Class of Stock [Line Items]
Tax receivable agreement, coverage percentage			130.00%
Retailco and NuDevco Retail | Common Class A
Class of Stock [Line Items]
Tax receivable agreement, target dividend (in dollars per share) | $ / shares			$ 0.18125
Retailco and NuDevco Retail | Series A Preferred Stock
Class of Stock [Line Items]
Tax receivable agreement, target dividend (in dollars per share) | $ / shares			$ 0.546875
Censtar Note | Convertible Debt | CenStar Earnout
Class of Stock [Line Items]
Contingent consideration—earnout obligations incurred in connection with the acquisitions | $		$ 2,100,000	$ 2,100,000
Oasis Note | Convertible Debt | Oasis Power Holdings
Class of Stock [Line Items]
Contingent consideration—earnout obligations incurred in connection with the acquisitions | $	$ 5,000,000		5,000,000
Tax Receivable Agreement | Retailco and NuDevco Retail
Class of Stock [Line Items]
Tax receivable agreement payment | $			$ 1,400,000	$ 1,400,000

Basis of Presentation and Sum40

Basis of Presentation and Summary of Significant Accounting Policies (Details)	Jun. 16, 2017	May 22, 2017	Dec. 31, 2017USD ($)		Dec. 31, 2017USD ($)segment		Dec. 31, 2016USD ($)		Dec. 31, 2015USD ($)
Finite-Lived Intangible Assets [Line Items]
Allowance for doubtful accounts			$ 4,000,000		$ 4,000,000		$ 2,300,000
Bad debt expense					6,550,000	[1]	1,261,000	[2]	$ 7,908,000	[3]
Inventory impairments					0		0		0
Customer acquisition costs, current			22,123,000		22,123,000		18,834,000
Customer acquisition costs, noncurrent			6,949,000	[4]	6,949,000	[4]	6,134,000
Amortization of acquisition costs					21,400,000		17,500,000		18,000,000
Intangible assets, current			18,653,000		18,653,000		12,113,000
Intangible assets, noncurrent			34,839,000		34,839,000		21,410,000
Impairment charges					$ 0		0		0
Goodwill impairment			0
Number of operating segments | segment					2
Gross receipts taxes					$ 9,000,000		5,300,000		3,000,000
Asset optimization revenue					178,300,000		133,000,000		154,100,000
Asset optimization costs of revenues					179,000,000		133,600,000		152,600,000
Stock split conversion ratio	2	2
Net excess tax benefits					200,000
Reclassification of acquisition related payments from cash flows from investing activities					97,757,000	[1]	36,344,000	[2]	41,943,000	[3]
Reclassification of acquisition related payments to cash flows from operating activities					63,912,000	[1]	67,793,000	[2]	45,931,000	[3]
Reclassification of acquisition related payments to cash flows from financing activities					44,304,000	[1]	(16,963,000)	[2]	(3,873,000)	[3]
Accounting Standards Update 2016-09
Finite-Lived Intangible Assets [Line Items]
Reclassification of acquisition related payments to cash flows from financing activities					1,100,000
Accounting Standards Update 2016-15
Finite-Lived Intangible Assets [Line Items]
Reclassification of acquisition related payments to cash flows from operating activities					1,800,000		800,000
Reclassification of acquisition related payments to cash flows from financing activities					18,400,000		2,000,000
Other current assets
Finite-Lived Intangible Assets [Line Items]
Gas balancing receivable (payable)			700,000		700,000		900,000
Other current liabilities
Finite-Lived Intangible Assets [Line Items]
Gas balancing receivable (payable)			(1,000,000)		$ (1,000,000)		(100,000)
Capitalized direct advertising costs
Finite-Lived Intangible Assets [Line Items]
Average useful life					2 years
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Impairment charges					$ 0		0		0
Customer Relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period					3 years
Customer Relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period					6 years
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Amortization expense					$ 17,800,000		28,600,000		5,700,000
Customer Relationships | Retail cost of revenue
Finite-Lived Intangible Assets [Line Items]
Amortization expense									0
Customer Relationships and Non-compete Agreements
Finite-Lived Intangible Assets [Line Items]
Amortization expense					15,021,000		27,157,000		4,503,000
Customer Relationships and Non-compete Agreements | Retail cost of revenue
Finite-Lived Intangible Assets [Line Items]
Amortization expense					$ 300,000		15,800,000		0
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Amortization period					3 years
Non-compete agreements | Provider Companies and Major Energy Companies
Finite-Lived Intangible Assets [Line Items]
Intangible assets, current			1,200,000		$ 1,200,000
Intangible assets, noncurrent			1,400,000		1,400,000
Amortization expense					1,200,000		900,000
Trademarks
Finite-Lived Intangible Assets [Line Items]
Intangible assets, noncurrent			$ 8,600,000		8,600,000		6,300,000
Amortization expense					$ 781,000		357,000		$ 74,000
Trademarks | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period					5 years
Trademarks | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period					20 years
Investing Activities to Operating Activities | Accounting Standards Update 2016-15
Finite-Lived Intangible Assets [Line Items]
Reclassification of acquisition related payments from cash flows from investing activities					$ 1,800,000		800,000
Investing Activities to Financing Activities | Accounting Standards Update 2016-15
Finite-Lived Intangible Assets [Line Items]
Reclassification of acquisition related payments from cash flows from investing activities					$ 18,400,000		$ 2,000,000
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.
[4]	See Note 4 "Equity" for disclosure of our variable interest entity in Spark HoldCo, LLC.

Basis of Presentation and Sum41

Basis of Presentation and Summary of Significant Accounting Policies - Non-controlling Interest (Details) - shares	Jan. 31, 2017	Jan. 08, 2017	Oct. 05, 2016	Dec. 31, 2017	Dec. 31, 2016
CenStar Note | Common Class B
Subsidiary, Sale of Stock [Line Items]
Number of shares, irrevocable commitment to convert (in shares)		269,462	269,462
Oasis Note | Common Class B
Subsidiary, Sale of Stock [Line Items]
Number of shares, irrevocable commitment to convert (in shares)	766,180		766,180
Spark HoldCo
Subsidiary, Sale of Stock [Line Items]
Economic interests percentage				38.12%	38.85%
NuDevco Retail Holdings | Spark HoldCo
Subsidiary, Sale of Stock [Line Items]
Economic interests percentage				61.88%	61.15%

Acquisitions - Acquisition of C

Acquisitions - Acquisition of CenStar Energy Corp - Narrative (Details) - USD ($) $ in Thousands	Jul. 08, 2015	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015		Mar. 31, 2016
Business Acquisition [Line Items]
EBITDA attributable to operations, earn-out				$ 22,700
Revenues		$ 798,055	[1]	546,697	[2]	$ 358,153	[3]
Operating loss		(102,420)	[1]	$ (84,001)	[2]	(29,905)	[3]
CenStar Earnout
Business Acquisition [Line Items]
Purchase price	$ 8,300
EBITDA attributable to operations, earn-out	500							$ 1,500
Revenues						21,400
Operating loss						1,400
Acquisition costs						$ 100
CenStar Earnout | Senior Secured Revolving Credit Facility
Business Acquisition [Line Items]
Initial working capital estimate	10,400
Contingent consideration—earnout obligations incurred in connection with the acquisitions	16,600
CenStar Earnout | Convertible Debt | Censtar Convertible Debt
Business Acquisition [Line Items]
Contingent consideration—earnout obligations incurred in connection with the acquisitions	$ 2,100	$ 2,100
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Acquisitions - Acquisition of O

Acquisitions - Acquisition of Oasis Power Holdings, LLC - Narrative (Details)	Jul. 31, 2015USD ($)stateutility	Dec. 31, 2017USD ($)		Dec. 31, 2016USD ($)	[2]	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Revenues		$ 798,055,000	[1]	$ 546,697,000		$ 358,153,000	[3]
Operating loss		(102,420,000)	[1]	$ (84,001,000)		(29,905,000)	[3]
Oasis
Business Acquisition [Line Items]
Number of states in which company operates | state	6
Number of utilities | utility	18
Purchase price	$ 20,000,000
Purchase price, payments from cash on hand	2,000,000
Revenues						26,900,000
Operating loss						$ 500,000
Oasis | Senior Secured Revolving Credit Facility
Business Acquisition [Line Items]
Contingent consideration—earnout obligations incurred in connection with the acquisitions	15,000,000
Oasis | Convertible Debt | Oasis Note
Business Acquisition [Line Items]
Contingent consideration—earnout obligations incurred in connection with the acquisitions	$ 5,000,000	$ 5,000,000
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Acquisitions - Acquisition of P

Acquisitions - Acquisition of Provider Companies - Narrative (Details)	Aug. 01, 2016USD ($)payment$ / sharesshares	Dec. 31, 2017USD ($)		Dec. 31, 2016USD ($)		Dec. 31, 2015USD ($)	[3]	Aug. 23, 2016$ / shares
Business Acquisition [Line Items]
Installment payment		$ 152,939,000	[1]	$ 66,652,000	[2]	$ 49,826,000
Common Class B
Business Acquisition [Line Items]
Issuance of stock to affiliates		0	[1]	40,000,000	[2]	0
Share price (in dollars per share) | $ / shares	$ 10							$ 10
Provider Companies
Business Acquisition [Line Items]
Purchase price	$ 34,100,000
Initial working capital estimate	1,300,000
Installment consideration payment	$ 3,800,000	0	[1]	1,890,000	[2]	$ 0
Frequency of monthly payments | payment	10
Installment payment	$ 400,000
Revenue				46,800,000
Operating loss				$ 12,800,000
Provider Companies | Common Class B
Business Acquisition [Line Items]
Shares issued (shares) | shares	1,399,484
Issuance of stock to affiliates	$ 14,000,000
Revolving Credit Facility | Acquisition Line | Provider Companies
Business Acquisition [Line Items]
Borrowing from credit facility	10,600,000
Recurring | Provider Companies
Business Acquisition [Line Items]
Contingent consideration—earnout obligations incurred in connection with the acquisitions		$ 4,800,000
Maximum | Provider Companies
Business Acquisition [Line Items]
Earnout amount	$ 9,000,000
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.

Acquisitions - Acquisition of45

Acquisitions - Acquisition of Provider Companies (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 120,154	$ 79,147	$ 18,379	$ 0
Provider Companies
Business Acquisition [Line Items]
Cash		431
Net working capital, net of cash acquired		812
Goodwill		26,040
Fair value of derivative liabilities		(18,163)
Total		34,066
Provider Companies | Customer Relationships and Non-compete Agreements
Business Acquisition [Line Items]
Intangible assets		24,417
Provider Companies | Trademarks
Business Acquisition [Line Items]
Intangible assets		$ 529

Acquisitions - Acquisition of M

Acquisitions - Acquisition of Major Energy Companies - Narrative (Details)	Aug. 23, 2016USD ($)utility$ / sharesshares	Dec. 31, 2017USD ($)		Dec. 31, 2016USD ($)		Dec. 31, 2015USD ($)	[3]	Aug. 01, 2016$ / shares	Apr. 15, 2016USD ($)
Business Acquisition [Line Items]
Amount recorded as equity transaction		$ 0	[1]	$ 3,873,000	[2]	$ 0
Major Energy Companies
Business Acquisition [Line Items]
Number of utilities | utility	43
Consideration amount	$ 64,100,000
Working capital	5,200,000
Litigation reserve	5,000,000
Installment and earnout payments (up to)	35,000,000
Installment and earnout payments purchase date value									$ 13,100,000
Amount recorded as equity transaction	3,900,000
Contributed revenues		125,600,000
Contributed earnings		1,300,000
Major Energy Companies
Business Acquisition [Line Items]
Employment contract termination costs				4,100,000
Paid employment contract termination costs		2,500,000
Liability related to contract termination costs		$ 1,600,000
Contract termination costs payment period		22 months
Major Energy Companies | Major Energy Companies
Business Acquisition [Line Items]
Working capital	$ 4,300,000
Working capital settled		$ 5,200,000
Amount recorded as equity transaction		900,000
Common Class B
Business Acquisition [Line Items]
Share price (in dollars per share) | $ / shares	$ 10							$ 10
Common Class B | Major Energy Companies
Business Acquisition [Line Items]
Share amount maximum (in shares) | shares	81,436
Value of shares for earnout		$ 0		$ 800,000
Value of shares issued for acquisition	$ 40,000,000
Common Class B | Major Energy Companies
Business Acquisition [Line Items]
Number of shares issued for acquisition (in shares) | shares	4,000,000
Maximum | Common Class B | Major Energy Companies
Business Acquisition [Line Items]
Share amount maximum (in shares) | shares	400,000
National Gas & Electric, LLC | Major Energy Companies
Business Acquisition [Line Items]
Initial working capital estimate	$ 300,000
Working capital settled	$ 10,600,000
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.

Acquisitions - Acquisition of47

Acquisitions - Acquisition of Major Energy Companies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 120,154	$ 79,147	$ 18,379	$ 0
National Gas & Electric, LLC | Major Energy Companies
Business Acquisition [Line Items]
Cash	17,368	17,368
Property and equipment	14	14
Non-current deferred tax assets	1,042	1,042
Goodwill	34,988	34,728
Net working capital, net of cash acquired	(6,746)	(6,746)
Fair value of derivative liabilities	(7,260)	(7,260)
Total	68,650	68,390
2017 Adjustments
Goodwill	260
Net working capital, net of cash acquired	0
Total	260
Customer Relationships | National Gas & Electric, LLC | Major Energy Companies
Business Acquisition [Line Items]
Intangible assets - customer relationships & non-compete agreements	24,271	24,271
Trademarks | National Gas & Electric, LLC | Major Energy Companies
Business Acquisition [Line Items]
Other assets - trademarks	$ 4,973	$ 4,973

Acquisitions - Pro Forma Inform

Acquisitions - Pro Forma Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Verde Companies
Business Acquisition [Line Items]
Revenue	$ 868,415	$ 716,696
Earnings	$ 18,047	17,860
National Gas & Electric, LLC | Major Energy Companies
Business Acquisition [Line Items]
Revenue		603,673	$ 547,381
Earnings		$ 15,776	$ 15,460

Acquisitions - Acquisition of49

Acquisitions - Acquisition of Perigree - Narrative (Details) - National Gas & Electric, LLC - Perigee Energy, LLC $ in Millions	Apr. 01, 2017USD ($)utility
Business Acquisition [Line Items]
Number of utilities | utility	14
Purchase price	$ 4.1
Purchase price, base price	2
Purchase price, additional customer option payment	0.2
Initial working capital estimate	$ 1.9

Acquisitions - Acquisition of50

Acquisitions - Acquisition of Perigree (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 120,154	$ 79,147	$ 18,379	$ 0
National Gas & Electric, LLC | Perigee Energy, LLC
Business Acquisition [Line Items]
Cash	23
Goodwill	1,540
Net working capital, net of cash acquired	2,085
Fair value of derivative liabilities	(443)
Total	4,305
Customer Relationships | National Gas & Electric, LLC | Perigee Energy, LLC
Business Acquisition [Line Items]
Intangible assets	$ 1,100

Acquisitions - Acquisition of V

Acquisitions - Acquisition of Verde - Narrative (Details) - USD ($)	Jul. 01, 2017	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015	[3]	Jan. 12, 2018
Business Acquisition [Line Items]
Promissory note payable		$ 145,744,000		$ 78,370,000
Accretion on fair value of Earnout liabilities		4,108,000	[1]	$ 5,060,000	[2]	$ 0
Verde Companies
Business Acquisition [Line Items]
Total consideration	$ 91,200,000
Net working capital	20,800,000	500,000
Consideration funded	85,800,000
Payments to acquire business	6,800,000
Contingent consideration—earnout obligations incurred in connection with the Provider Companies and Major Energy Companies acquisitions	$ 5,400,000
Earnout period	18 months
Adjusted EBITDA obligation, percent	100.00%
Adjusted EBITDA obligation term	18 months
Subordinated Debt | Verde Companies
Business Acquisition [Line Items]
Contingent consideration—earnout obligations incurred in connection with the Provider Companies and Major Energy Companies acquisitions	$ 15,000,000
Revolving Credit Facility | Verde Companies
Business Acquisition [Line Items]
Contingent consideration—earnout obligations incurred in connection with the Provider Companies and Major Energy Companies acquisitions	44,000,000
Notes Payable | Verde Companies
Business Acquisition [Line Items]
Contingent consideration—earnout obligations incurred in connection with the Provider Companies and Major Energy Companies acquisitions	$ 20,000,000
Notes Payable | Verde Earnout Termination Note
Business Acquisition [Line Items]
Promissory note payable		5,900,000
Subsequent Event | Notes Payable | Verde Earnout Termination Note
Business Acquisition [Line Items]
Promissory note payable								$ 5,900,000
National Gas & Electric, LLC | Verde Companies
Business Acquisition [Line Items]
Increase in fair value recorded in general and administrative expense		300,000
Verde Earnout
Business Acquisition [Line Items]
Accretion on fair value of Earnout liabilities		200,000
Verde Companies
Business Acquisition [Line Items]
Contributed revenues		76,000,000
Contributed earnings		$ 1,200,000
Trademarks | Verde Companies
Business Acquisition [Line Items]
Amortization period		5 years
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.

Acquisitions - Acquisition of52

Acquisitions - Acquisition of Verde (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 120,154	$ 79,147	$ 18,379	$ 0
Verde Companies
Business Acquisition [Line Items]
Cash	1,653
Property and equipment	4,560
Goodwill	39,207
Net working capital, net of cash acquired	19,132
Deferred tax liability	(3,126)
Fair value of derivative liabilities	(1,942)
Total	91,184
Customer Relationships | Verde Companies
Business Acquisition [Line Items]
Intangible assets	28,700
Trademarks | Verde Companies
Business Acquisition [Line Items]
Intangible assets	$ 3,000

Equity - Non-controlling Intere

Equity - Non-controlling Interest (Details) - USD ($) $ in Thousands	Jan. 31, 2017	Jan. 08, 2017	Oct. 05, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Class of Stock [Line Items]
Net income allocated to non-controlling interest				$ 56,696		$ 52,300		$ 21,779
Income tax expense (benefit) allocated to non-controlling interest				(731)		1,071		(331)
Net income attributable to non-controlling interest				$ 57,427	[1]	$ 51,229	[2]	$ 22,110	[3]
CenStar Note | Common Class B
Class of Stock [Line Items]
Number of shares, irrevocable commitment to convert (in shares)		269,462	269,462
Oasis Note | Common Class B
Class of Stock [Line Items]
Number of shares, irrevocable commitment to convert (in shares)	766,180		766,180
Spark HoldCo
Class of Stock [Line Items]
Economic interests percentage				38.12%		38.85%
Spark HoldCo | NuDevco Retail and Retailco LLC
Class of Stock [Line Items]
Economic interests percentage				61.88%		61.15%
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Equity - Narrative (Details)

Equity - Narrative (Details)

Jun. 16, 2017

May 22, 2017

Jan. 31, 2017shares

Jan. 08, 2017shares

Oct. 05, 2016shares

Aug. 01, 2016shares

Jun. 08, 2016shares

Apr. 01, 2016shares

Feb. 03, 2016shares

Dec. 31, 2017USD ($)vote$ / sharesshares

Dec. 31, 2016shares

May 24, 2017USD ($)

Class of Stock [Line Items]

Stock split conversion ratio

2

2

Treasury stock, shares (in shares)

99,446

0

Number of shares of common stock exchanged (in shares)

1,000,000

3,450,000

2,000,000

Preferred stock, shares authorized (in shares)

20,000,000

Preferred stock, shares issued (in shares)

1,704,339

0

Preferred stock, shares outstanding (in shares)

1,704,339

0

Common Class A

Class of Stock [Line Items]

Common stock, shares outstanding (in shares)

13,135,636

12,993,118

Common stock voting rights ratio | vote

1

Common Class B

Class of Stock [Line Items]

Common stock, shares outstanding (in shares)

21,485,126

20,449,484

Common stock voting rights ratio | vote

1

Restricted Stock Units

Class of Stock [Line Items]

Number of shares vested (in shares)

356,014

395,056

Number of shares of common stock distributed to the holder of restricted stock units (in shares)

241,965

305,872

Number of shares of common stock withheld to cover taxes owed on vested units (in shares)

114,049

89,184

Provider Companies | Common Class B

Class of Stock [Line Items]

Number of shares issued for acquisition (in shares)

1,399,484

CenStar Note | Common Class B

Class of Stock [Line Items]

Number of shares, irrevocable commitment to convert (in shares)

269,462

269,462

Oasis Note | Common Class B

Class of Stock [Line Items]

Number of shares, irrevocable commitment to convert (in shares)

766,180

766,180

Share Repurchase Program

Class of Stock [Line Items]

Treasury stock repurchased, weighted-average price (in dollars per share) | $ / shares

$ 20.22

Share Repurchase Program | Common Class A

Class of Stock [Line Items]

Stock repurchase program, authorized amount | $

$ 50,000,000

Shares repurchased (in shares)

99,446

Treasury stock, total cost of shares repurchased | $

$ 2,000,000

Equity - Earnings per Share (De

Equity - Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		Jan. 31, 2017	Jan. 08, 2017	Oct. 05, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Spark Energy, Inc. stockholders					$ 18,854	[1]	$ 14,444	[2]	$ 3,865	[3]
Less: Dividend on Series A preferred stock	[1]				3,038		0	[2]	0	[3]
Net income attributable to stockholders of Class A common stock					$ 15,816	[1]	$ 14,444	[2]	$ 3,865	[3]
Basic weighted average Class A common shares outstanding (in shares)					13,143,000	[1]	11,402,000	[2]	6,129,000	[3]
Basic EPS attributable to stockholders (in dollars per share)					$ 1.20	[1]	$ 1.27	[2]	$ 0.63	[3]
Effect of conversion of Class B common stock to shares of Class A common stock					$ 0		$ 0		$ 0
Effect of conversion of convertible subordinated notes into shares of Class B common stock and shares of Class B common stock into shares of Class A common stock					0		(310)		(334)
Diluted net income attributable to stockholders of Class A common stock					$ 15,816		$ 14,134		$ 3,531
Basic weighted average Class A common shares outstanding (in shares)					13,143,000	[1]	11,402,000	[2]	6,129,000	[3]
Effect of dilutive Class B common stock (in shares)					0		0		0
Effect of conversion of convertible subordinated notes into shares of Class B common stock and shares of Class B common stock into shares of Class A common stock (in shares)					0		1,010,000		420,000
Effect of dilutive restricted stock units (in shares)					203,000		278,000		106,000
Diluted weighted average shares outstanding (in shares)					13,346,000	[1]	12,690,000	[2]	6,655,000	[3]
Diluted EPS attributable to stockholders (in dollars per share)					$ 1.19	[1]	$ 1.11	[2]	$ 0.53	[3]
CenStar Note | Common Class B
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Number of shares, irrevocable commitment to convert (in shares)			269,462	269,462
Oasis Note | Common Class B
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Number of shares, irrevocable commitment to convert (in shares)		766,180		766,180
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Equity - Classification of Asse

Equity - Classification of Assets and Liabilities (Details) - Variable Interest Entity, Primary Beneficiary $ in Thousands	Dec. 31, 2017USD ($)
Variable Interest Entity [Line Items]
Total Assets	$ 476,070
Total Liabilities	249,648
Total current assets
Variable Interest Entity [Line Items]
Total Assets	293,364
Cash and cash equivalents
Variable Interest Entity [Line Items]
Total Assets	29,385
Accounts receivable
Variable Interest Entity [Line Items]
Total Assets	158,814
Other current assets
Variable Interest Entity [Line Items]
Total Assets	105,165
Total non-current assets
Variable Interest Entity [Line Items]
Total Assets	182,706
Goodwill
Variable Interest Entity [Line Items]
Total Assets	120,154
Other assets
Variable Interest Entity [Line Items]
Total Assets	62,552
Total current liabilities
Variable Interest Entity [Line Items]
Total Liabilities	130,609
Accounts Payable and Accrued Liabilities
Variable Interest Entity [Line Items]
Total Liabilities	110,152
Current portion of Senior Credit Facility
Variable Interest Entity [Line Items]
Total Liabilities	7,500
Contingent consideration
Variable Interest Entity [Line Items]
Total Liabilities	4,024
Other current liabilities
Variable Interest Entity [Line Items]
Total Liabilities	8,933
Total long-term liabilities
Variable Interest Entity [Line Items]
Total Liabilities	119,039
Long-term portion of Senior Credit Facility
Variable Interest Entity [Line Items]
Total Liabilities	117,750
Contingent consideration
Variable Interest Entity [Line Items]
Total Liabilities	626
Other long-term liabilities
Variable Interest Entity [Line Items]
Total Liabilities	$ 663

Preferred Stock (Details)

Preferred Stock (Details) - USD ($)	Jan. 26, 2018	Jan. 23, 2018	Mar. 15, 2017	Mar. 09, 2018	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015	[3]	Jul. 21, 2017
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)					1,704,339		0
Preferred stock, shares outstanding (in shares)					1,704,339		0
Preferred stock, par value per share (in dollars per share)					$ 0.01		$ 0.01
Net proceeds from offering			$ 39,000,000		$ 40,241,000	[1]	$ 0	[2]	$ 0
Offering expenses			$ 1,000,000
Aggregate offering price											$ 50,000,000
Dividends paid					$ 3,038,000
Subsequent Event
Class of Stock [Line Items]
Net proceeds from offering	$ 48,900,000			$ 48,900,000
London Interbank Offered Rate (LIBOR)
Class of Stock [Line Items]
Preferred stock, dividend accrual rate			6.578%
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)					1,704,339		0
Preferred stock, shares outstanding (in shares)
Preferred stock, par value per share (in dollars per share)			$ 0.01
Preferred stock, liquidation preference (in dollars per share)			25
Preferred stock, price to the public (in dollars per share)			25
Preferred stock, price, net of underwriting discounts and commissions (in dollars per share)			$ 24.21
Shares issued (in shares)			1,610,000
Preferred stock, dividend accrual rate			8.75%
Dividends paid					$ 2,100,000
Dividend accrual					900,000
Series A Preferred Stock | Subsequent Event
Class of Stock [Line Items]
Shares issued (in shares)	2,000,000
Preferred stock, dividend accrual rate		8.75%
Series A Preferred Stock | ATM Agreement
Class of Stock [Line Items]
Net proceeds from offering					2,400,000
Offering expenses					$ 100,000
Shares issued (in shares)					94,339
Over-Allotment Option [Member] | Subsequent Event
Class of Stock [Line Items]
Period of option to purchase additional shares		30 days
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.

Preferred Stock - Summary of Me

Preferred Stock - Summary of Mezzanine Equity (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Increase (Decrease) in Temporary Equity [Roll Forward]
Mezzanine equity at December 31, 2016	$ 0
Issuance of Series A Preferred Stock, net of issuance cost	40,241
Accumulated dividends on Series A Preferred Stock	932
Mezzanine equity at December 31, 2017	$ 41,173

Property and Equipment - Compon

Property and Equipment - Components (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total	$ 41,444	$ 35,267
Accumulated depreciation	(33,169)	(30,561)
Property and equipment—net	8,275	4,706
Information technology
Property, Plant and Equipment [Line Items]
Total	$ 34,103	29,675
Information technology | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	2 years
Information technology | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total	$ 4,568	4,568
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	2 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	$ 1,964	1,024
Furniture and fixtures | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	2 years
Furniture and fixtures | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years
Building improvements
Property, Plant and Equipment [Line Items]
Total	$ 809	$ 0
Building improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	2 years
Building improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	5 years

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 2.6	$ 2.1	$ 1.6
Information technology
Property, Plant and Equipment [Line Items]
Assets not yet placed into service	$ 1.2	$ 1.1

Goodwill, Customer Relationsh61

Goodwill, Customer Relationships and Trademarks - Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 120,154	$ 79,147	$ 18,379	$ 0
Finite-Lived Intangible Assets [Line Items]
Total	62,050
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Cost	93,371	63,571
Accumulated amortization	(46,681)	(31,660)
Total	46,690	31,911
Customer Relationships— Other
Finite-Lived Intangible Assets [Line Items]
Cost	12,336	4,320
Accumulated amortization	(5,534)	(2,708)
Total	6,802	1,612	3,049	1,501
Trademarks
Finite-Lived Intangible Assets [Line Items]
Cost	9,770	6,770
Accumulated amortization	(1,212)	(431)
Total	$ 8,558	$ 6,339	$ 1,194	$ 0

Goodwill, Customer Relationsh62

Goodwill, Customer Relationships and Trademarks - Roll Forward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Balance at beginning of period	$ 79,147	$ 18,379	$ 0
Acquisitions	260	0	0
Balance at end of period	120,154	79,147	18,379
Finite-lived Intangible Assets [Roll Forward]
Balance at end of period	62,050
Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	1,612	3,049	1,501
Acquisitions	0	0	2,731
Amortization expense	(2,826)	(1,437)	(1,183)
Balance at end of period	6,802	1,612	3,049
Trademarks
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	6,339	1,194	0
Acquisitions	0	0	0
Amortization expense	(781)	(357)	(74)
Balance at end of period	8,558	6,339	1,194
Customer Relationships— Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Balance at beginning of period	31,911	10,380	0
Acquisitions	0	0	0
Amortization expense	(15,021)	(27,157)	(4,503)
Balance at end of period	46,690	31,911	10,380
CenStar Earnout
Goodwill [Roll Forward]
Acquisitions			6,396
CenStar Earnout | Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Acquisitions			0
CenStar Earnout | Trademarks
Finite-lived Intangible Assets [Roll Forward]
Acquisitions			651
CenStar Earnout | Customer Relationships— Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Acquisitions			5,494
Oasis
Goodwill [Roll Forward]
Acquisitions			11,983
Oasis | Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Acquisitions			0
Oasis | Trademarks
Finite-lived Intangible Assets [Roll Forward]
Acquisitions			617
Oasis | Customer Relationships— Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Acquisitions			$ 9,389
Provider Companies
Goodwill [Roll Forward]
Balance at beginning of period	26,040
Acquisitions		26,040
Balance at end of period		26,040
Provider Companies | Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Acquisitions		0
Provider Companies | Trademarks
Goodwill [Roll Forward]
Intangible assets		529
Provider Companies | Customer Relationships— Acquired & Non-Compete Agreements
Goodwill [Roll Forward]
Intangible assets		24,417
Major Energy Companies
Goodwill [Roll Forward]
Acquisitions		34,728
Major Energy Companies | Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Acquisitions		0
Major Energy Companies | Trademarks
Finite-lived Intangible Assets [Roll Forward]
Acquisitions		4,973
Major Energy Companies | Customer Relationships— Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Acquisitions		$ 24,271
Perigee
Goodwill [Roll Forward]
Acquisitions	1,540
Perigee | Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	0
Perigee | Trademarks
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	0
Perigee | Customer Relationships— Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	1,100
Verde Companies
Goodwill [Roll Forward]
Acquisitions	39,207
Balance at end of period	39,207
Verde Companies | Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	0
Verde Companies | Trademarks
Goodwill [Roll Forward]
Intangible assets	3,000
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	3,000
Verde Companies | Customer Relationships— Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	28,700
GAP | Customer Relationships— Other
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	8,016
GAP | Trademarks
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	0
GAP | Customer Relationships— Acquired & Non-Compete Agreements
Finite-lived Intangible Assets [Roll Forward]
Acquisitions	$ 0

Goodwill, Customer Relationsh63

Goodwill, Customer Relationships and Trademarks - Narrative (Details) - Customer Relationships and Non-compete Agreements - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 15,021,000	$ 27,157,000	$ 4,503,000
Cost of revenue
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 300,000	$ 15,800,000	$ 0

Goodwill, Customer Relationsh64

Goodwill, Customer Relationships and Trademarks - Future Amortization Expense (Details) $ in Thousands	Dec. 31, 2017USD ($)
Year Ending December 31,
2,018	$ 19,469
2,019	14,894
2,020	10,474
2,021	8,912
2,022	4,700
More than 5 years	3,601
Total	$ 62,050

Debt - Components of Debt (Deta

Debt - Components of Debt (Details) - USD ($) $ in Thousands	Jan. 31, 2017	Jan. 08, 2017	Oct. 05, 2016	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total current debt				$ 20,943	$ 73,370
Total long-term debt				124,801	5,000
Total debt				145,744	78,370
Senior Credit Facility
Debt Instrument [Line Items]
Letters of credit issued					$ 29,600
Weighted average interest rate on current portion of debt					4.93%
Senior Credit Facility | Bridge Loan
Debt Instrument [Line Items]
Total current debt				7,500	$ 0
Senior Credit Facility | Acquisition Line
Debt Instrument [Line Items]
Total long-term debt				117,750	0
Letters of credit issued				$ 47,200
Weighted average interest rate on current portion of debt				4.61%
Notes Payable | Pacific Summit Energy
Debt Instrument [Line Items]
Total current debt				$ 0	15,501
Notes Payable | Verde
Debt Instrument [Line Items]
Total current debt				13,443	0
Total long-term debt				7,051	0
Convertible Debt
Debt Instrument [Line Items]
Total current debt				0	6,582
Subordinated Debt
Debt Instrument [Line Items]
Total long-term debt				0	5,000
Senior Credit Facility | Working Capital Line
Debt Instrument [Line Items]
Total current debt				0	29,000
Senior Credit Facility | Acquisition Line
Debt Instrument [Line Items]
Total current debt				$ 0	$ 22,287
Common Class B | CenStar Note
Debt Instrument [Line Items]
Number of shares, irrevocable commitment to convert (in shares)		269,462	269,462
Common Class B | Oasis Note
Debt Instrument [Line Items]
Number of shares, irrevocable commitment to convert (in shares)	766,180		766,180

Debt - Narrative (Details)

Debt - Narrative (Details)

Jul. 01, 2017USD ($)payment

Jan. 31, 2017USD ($)shares

Jan. 08, 2017shares

Dec. 27, 2016USD ($)

Oct. 05, 2016shares

Jul. 31, 2015USD ($)$ / shares

Dec. 31, 2017USD ($)shares

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Sep. 30, 2016USD ($)

Dec. 31, 2017USD ($)trade_credit_arrangementshares

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

[3]

Jan. 23, 2018USD ($)

Jan. 12, 2018USD ($)

Jan. 11, 2018USD ($)

Nov. 30, 2017USD ($)

Nov. 02, 2017USD ($)

Aug. 01, 2017

May 19, 2017USD ($)

Sep. 29, 2016USD ($)

Jul. 08, 2015USD ($)

May 12, 2015$ / shares

Debt Instrument [Line Items]

Deferred financing costs

$ 1,600,000

$ 1,600,000

$ 400,000

Convertible subordinated notes to affiliates

0

0

6,582,000

Interest expense

11,134,000

[1]

8,859,000

[2]

$ 2,280,000

Subordinated debt, noncurrent

0

0

5,000,000

Current portion of note payable

13,443,000

13,443,000

15,501,000

Promissory note payable

145,744,000

145,744,000

78,370,000

Current maturities of debt

20,943,000

20,943,000

73,370,000

Other current assets

Debt Instrument [Line Items]

Deferred financing costs

1,200,000

1,200,000

400,000

Other Noncurrent Assets

Debt Instrument [Line Items]

Deferred financing costs

400,000

400,000

0

Revolving Credit Facility

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 185,000,000

$ 200,000,000

$ 120,000,000

Line of credit facility, outstanding

125,300,000

125,300,000

Line of credit facility, available borrowing capacity

12,500,000

12,500,000

Letters of credit issued

$ 47,200,000

$ 47,200,000

Working Capital Line | Revolving Credit Facility

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

200,000,000

$ 82,500,000

Repayment percent

6.25%

6.25%

6.25%

6.25%

25.00%

Nonutilization fee

0.50%

Acquisition Line | Revolving Credit Facility

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 25,000,000

Financing of cost of acquisitions, maximum percentage

75.00%

Bridge Loan | Revolving Credit Facility

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 50,000,000

Senior Secured Revolving Credit Facility

Debt Instrument [Line Items]

Maximum leverage ratio

200.00%

Debt default, material judgment (in excess of)

$ 5,000,000

Subsequent Event | Senior Credit Facility

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 200,000,000

$ 150,000,000

Letters of credit issued

$ 5,000,000

$ 10,000,000

Eurodollar | Working Capital Line | Revolving Credit Facility

Debt Instrument [Line Items]

Basis spread on variable rate

3.00%

Base Rate | Working Capital Line | Revolving Credit Facility

Debt Instrument [Line Items]

Basis spread on variable rate

2.00%

Federal Funds Rate | Working Capital Line | Revolving Credit Facility

Debt Instrument [Line Items]

Basis spread on variable rate

0.50%

Federal Funds Rate | Acquisition Line | Revolving Credit Facility

Debt Instrument [Line Items]

Basis spread on variable rate

0.50%

Reference Eurodollar Rate | Working Capital Line | Revolving Credit Facility

Debt Instrument [Line Items]

Basis spread on variable rate

1.00%

Reference Eurodollar Rate | Acquisition Line | Revolving Credit Facility

Debt Instrument [Line Items]

Basis spread on variable rate

1.00%

Minimum | Senior Secured Revolving Credit Facility

Debt Instrument [Line Items]

Fixed charge coverage ratio (not less than)

125.00%

Maximum | Eurodollar | Acquisition Line | Revolving Credit Facility

Debt Instrument [Line Items]

Basis spread on variable rate

3.75%

Maximum | Base Rate | Acquisition Line | Revolving Credit Facility

Debt Instrument [Line Items]

Basis spread on variable rate

2.75%

Common Class B | CenStar Note

Debt Instrument [Line Items]

Number of shares, irrevocable commitment to convert (in shares) | shares

269,462

269,462

Common Class B | Censtar Convertible Debt

Debt Instrument [Line Items]

Number of shares, irrevocable commitment to convert (in shares) | shares

269,462

Common Class B | Oasis Note

Debt Instrument [Line Items]

Number of shares, irrevocable commitment to convert (in shares) | shares

766,180

766,180

Common Class A

Debt Instrument [Line Items]

Shares issued, price per share (in dollars per share) | $ / shares

$ 8.11

Common Class A | Senior Secured Revolving Credit Facility

Debt Instrument [Line Items]

Number of shares entitled to repurchase (in shares) | shares

10,000,000

10,000,000

Common Class A and Common Class B | Senior Secured Revolving Credit Facility

Debt Instrument [Line Items]

Default share limit, minimum amount (in shares) | shares

13,600,000

13,600,000

Subordinated Debt | Retailco

Debt Instrument [Line Items]

Subordinated borrowing, interest rate

5.00%

Subordinated debt

$ 25,000,000

Subordinated debt, advances

$ 1,000,000

Subordinated debt, interest rate on advances

5.00%

Minimum availability under the borrowing base

$ 5,000,000

Notes Payable | Pacific Summit Energy

Debt Instrument [Line Items]

Current maturities of debt

$ 0

$ 0

15,501,000

Notes Payable | Verde Promissory Note

Debt Instrument [Line Items]

Stated percentage interest rate

5.00%

Debt issued

$ 20,000,000

Debt, monthly installments | payment

18,000

Promissory note payable

14,600,000

14,600,000

Current maturities of debt

13,400,000

13,400,000

Notes Payable | Verde Earnout Termination Note

Debt Instrument [Line Items]

Promissory note payable

5,900,000

5,900,000

Notes Payable | Subsequent Event | Verde Promissory Note

Debt Instrument [Line Items]

Stated percentage interest rate

9.00%

Notes Payable | Subsequent Event | Verde Earnout Termination Note

Debt Instrument [Line Items]

Promissory note payable

$ 5,900,000

Convertible Subordinated Notes | Censtar Convertible Debt

Debt Instrument [Line Items]

Stated percentage interest rate

5.00%

Convertible Subordinated Notes | Oasis Note

Debt Instrument [Line Items]

Stated percentage interest rate

5.00%

Conversion price per share (in dollars per share) | $ / shares

$ 7

Beneficial conversion feature

$ 800,000

Convertible Debt

Debt Instrument [Line Items]

Current maturities of debt

$ 0

$ 0

$ 6,582,000

Convertible Debt | Oasis Note

Debt Instrument [Line Items]

Interest expense

$ 1,000,000

CenStar | Convertible Subordinated Notes | Censtar Convertible Debt

Debt Instrument [Line Items]

Convertible subordinated notes to affiliates

$ 2,100,000

CenStar | Convertible Debt | Censtar Convertible Debt

Debt Instrument [Line Items]

Debt issued

$ 2,100,000

Oasis | Convertible Subordinated Notes | Oasis Note

Debt Instrument [Line Items]

Convertible subordinated notes to affiliates

5,000,000

Oasis | Convertible Debt | Oasis Note

Debt Instrument [Line Items]

Debt issued

$ 5,000,000

Major Energy Companies | Pacific Summit Energy

Debt Instrument [Line Items]

Number of trade credit arrangements | trade_credit_arrangement

3

Interest rate, effective percentage

4.00%

Major Energy Companies | London Interbank Offered Rate (LIBOR) | Pacific Summit Energy

Debt Instrument [Line Items]

Basis spread on variable rate

3.00%

[1]

Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[2]

Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[3]

Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Debt - Interest Expense (Detail

Debt - Interest Expense (Details) - USD ($)	5 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Line of Credit Facility [Line Items]
Accretion on fair value of Earnout liabilities			$ 4,108,000	[1]	$ 5,060,000	[2]	$ 0	[3]
Amortization of deferred financing costs			1,035,000		668,000		412,000
Interest expense			11,134,000	[4]	8,859,000	[5]	2,280,000	[6]
Convertible Subordinated Notes
Line of Credit Facility [Line Items]
Interest incurred on convertible subordinated notes to affiliate			1,052,000		518,000		207,000
Convertible Subordinated Notes | Oasis Note
Line of Credit Facility [Line Items]
Amortization of discount (less than)			0		200,000		100,000
Subordinated Debt
Line of Credit Facility [Line Items]
Interest incurred on long-term debt			167,000		0		0
Promissory Note
Line of Credit Facility [Line Items]
Interest incurred on long-term debt			372,000		0		0
Working Capital Facility
Line of Credit Facility [Line Items]
Letters of credit fees and commitment fees			1,125,000		883,000		517,000
Working Capital Facility | Senior Credit Facility
Line of Credit Facility [Line Items]
Interest incurred on long-term debt			3,275,000		1,730,000		1,144,000
Prior Senior Credit Facility | Senior Credit Facility
Line of Credit Facility [Line Items]
Write offs of deferred financing costs							100,000
Extinguishment of the Seventh Amended Credit Facility | Senior Credit Facility
Line of Credit Facility [Line Items]
Write offs of deferred financing costs							300,000
Execution of the Seventh Amended Credit Facility | Senior Credit Facility
Line of Credit Facility [Line Items]
Write offs of deferred financing costs							100,000
Provider Earnout
Line of Credit Facility [Line Items]
Accretion on fair value of Earnout liabilities	$ 100,000		100,000
Major Earnout
Line of Credit Facility [Line Items]
Accretion on fair value of Earnout liabilities		$ 5,000,000	3,800,000		4,900,000
Verde Earnout
Line of Credit Facility [Line Items]
Accretion on fair value of Earnout liabilities			200,000
Recurring | Level 3
Line of Credit Facility [Line Items]
Accretion on fair value of Earnout liabilities			4,108,000		5,060,000		$ 0
Recurring | Level 3 | Provider Earnout
Line of Credit Facility [Line Items]
Accretion on fair value of Earnout liabilities			107,000		70,000
Recurring | Level 3 | Verde Earnout
Line of Credit Facility [Line Items]
Accretion on fair value of Earnout liabilities			$ 153,000		$ 0
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.
[4]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[5]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[6]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangement		$ (22,700)
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	$ 34,500	11,427
Total commodity derivative liabilities	(2,129)	(748)
Contingent payment arrangement	(4,650)	(22,653)
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	158	1,612
Total commodity derivative liabilities	(942)	0
Contingent payment arrangement	0	0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	34,342	9,815
Total commodity derivative liabilities	(1,187)	(748)
Contingent payment arrangement	0	0
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	0	0
Total commodity derivative liabilities	0	0
Contingent payment arrangement	(4,650)	(22,653)	$ (500)
Non-trading Commodity Contract | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	34,044	10,896
Total commodity derivative liabilities	(1,337)	(661)
Non-trading Commodity Contract | Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	158	1,511
Total commodity derivative liabilities	(387)	0
Non-trading Commodity Contract | Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	33,886	9,385
Total commodity derivative liabilities	(950)	(661)
Non-trading Commodity Contract | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	0	0
Total commodity derivative liabilities	0	0
Trading Commodity Contract | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	456	531
Total commodity derivative liabilities	(792)	(87)
Trading Commodity Contract | Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	0	101
Total commodity derivative liabilities	(555)	0
Trading Commodity Contract | Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	456	430
Total commodity derivative liabilities	(237)	(87)
Trading Commodity Contract | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total commodity derivative assets	0	0
Total commodity derivative liabilities	$ 0	$ 0

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($)

Jul. 01, 2017

Aug. 23, 2016

Apr. 15, 2016

Jun. 30, 2017

Mar. 31, 2017

Aug. 31, 2016

Dec. 31, 2016

Dec. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

[3]

Jan. 12, 2018

Aug. 01, 2016

Mar. 31, 2016

Jul. 08, 2015

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent payment arrangement

$ (22,700,000)

$ (22,700,000)

$ (22,700,000)

Promissory note payable

78,370,000

78,370,000

$ 145,744,000

78,370,000

Contingent consideration, current

11,827,000

11,827,000

4,024,000

11,827,000

Contingent consideration, noncurrent

10,826,000

10,826,000

626,000

10,826,000

Change in fair value of Earnout liabilities

(7,898,000)

[1]

(297,000)

[2]

$ 0

Accretion on fair value of Earnout liabilities

4,108,000

[1]

5,060,000

[2]

$ 0

Recurring

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent payment arrangement

(22,653,000)

(22,653,000)

$ (4,650,000)

(22,653,000)

Provider Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Payment to sellers

$ 4,500,000

$ 1,000,000

Earnout period

9 months

Provider Companies | Recurring

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent consideration—earnout obligations incurred in connection with the Provider Companies and Major Energy Companies acquisitions

$ 4,800,000

CenStar Earnout

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent payment arrangement

$ (1,500,000)

$ (500,000)

Payment to sellers

$ 1,300,000

Release from escrow

$ 600,000

Major Energy Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Payment to sellers

$ 7,400,000

Verde Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Earnout period

18 months

Contingent consideration—earnout obligations incurred in connection with the Provider Companies and Major Energy Companies acquisitions

$ 5,400,000

General and Administrative Expense | CenStar Earnout

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Change in fair value of Earnout liabilities

(200,000)

National Gas & Electric, LLC | Provider Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Decrease in fair value recorded in general and administrative expense

500,000

National Gas & Electric, LLC | Major Energy Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Earnout period

33 months

Earnout amount

$ 20,000,000

17,800,000

17,800,000

4,600,000

17,800,000

Decrease in fair value recorded in general and administrative expense

9,600,000

1,100,000

National Gas & Electric, LLC | Verde Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Decrease in fair value recorded in general and administrative expense

300,000

Maximum | Provider Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Earnout amount

$ 9,000,000

Minimum | Provider Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Earnout amount

$ 5,000,000

Major Energy Companies | Common Class B

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Share amount maximum (in shares)

81,436

Major Energy Companies | Maximum | Common Class B

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Share amount maximum (in shares)

400,000

Provider Earnout

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent payment arrangement

(4,900,000)

(4,900,000)

(4,900,000)

Accretion on fair value of Earnout liabilities

100,000

100,000

Major Earnout

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent payment arrangement

(17,100,000)

(17,100,000)

(17,100,000)

Accretion on fair value of Earnout liabilities

5,000,000

3,800,000

4,900,000

Major Earnout | Recurring

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent payment arrangement

(4,600,000)

Major Earnout | Major Energy Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Accretion on fair value of Earnout liabilities

3,800,000

Stock Earnout

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent payment arrangement

(700,000)

(700,000)

(700,000)

Stock Earnout | Recurring

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent payment arrangement

0

Contingent consideration, current | Variable Interest Entity, Primary Beneficiary

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent consideration, current

11,800,000

11,800,000

4,000,000

11,800,000

Contingent consideration, noncurrent | Variable Interest Entity, Primary Beneficiary

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent consideration, noncurrent

$ 10,800,000

$ 10,800,000

600,000

$ 10,800,000

Notes Payable | Verde Companies

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Contingent consideration—earnout obligations incurred in connection with the Provider Companies and Major Energy Companies acquisitions

$ 20,000,000

Notes Payable | Verde Earnout Termination Note

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Promissory note payable

$ 5,900,000

Notes Payable | Subsequent Event | Verde Earnout Termination Note

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Promissory note payable

$ 5,900,000

[1]

Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[2]

Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[3]

Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.

Fair Value Measurements Liabili

Fair Value Measurements Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchase price contingent consideration, beginning balance		$ 22,700
Change in fair value of contingent consideration, net		(7,898)	[1]	$ (297)	[2]	$ 0	[3]
Accretion of contingent earnout consideration (included within interest expense)		4,108	[1]	5,060	[2]	0	[3]
Purchase price contingent consideration, ending balance	$ 22,700			22,700
Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchase price contingent consideration, beginning balance		22,653
Purchase price contingent consideration, ending balance	22,653	4,650		22,653
Recurring | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchase price contingent consideration, beginning balance		22,653		500
Purchase price contingent consideration, additions		5,400		18,733
Change in fair value of contingent consideration, net		(8,708)		(297)
Accretion of contingent earnout consideration (included within interest expense)		4,108		5,060		0
Payments and settlements		(18,803)		(1,343)
Purchase price contingent consideration, ending balance	22,653	4,650		22,653		500
CenStar Earnout | Recurring | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchase price contingent consideration, beginning balance		0		500
Purchase price contingent consideration, additions		0		0
Change in fair value of contingent consideration, net		0		843
Accretion of contingent earnout consideration (included within interest expense)		0		0
Payments and settlements		0		(1,343)
Purchase price contingent consideration, ending balance	0	0		0		500
Major Earnout and Stock Earnout | Recurring | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchase price contingent consideration, beginning balance		17,760		0
Purchase price contingent consideration, additions		0		13,910
Change in fair value of contingent consideration, net		(9,555)		(1,140)
Accretion of contingent earnout consideration (included within interest expense)		3,848		4,990
Payments and settlements		(7,403)		0
Purchase price contingent consideration, ending balance	17,760	4,650		17,760		0
Provider Earnout
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchase price contingent consideration, beginning balance		4,900
Accretion of contingent earnout consideration (included within interest expense)	100	100
Purchase price contingent consideration, ending balance	4,900			4,900
Provider Earnout | Recurring | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchase price contingent consideration, beginning balance		4,893		0
Purchase price contingent consideration, additions		0		4,823
Change in fair value of contingent consideration, net		500		0
Accretion of contingent earnout consideration (included within interest expense)		107		70
Payments and settlements		(5,500)		0
Purchase price contingent consideration, ending balance	4,893	0		4,893		0
Verde Earnout
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Accretion of contingent earnout consideration (included within interest expense)		200
Verde Earnout | Recurring | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Purchase price contingent consideration, beginning balance		0		0
Purchase price contingent consideration, additions		5,400		0
Change in fair value of contingent consideration, net		347		0
Accretion of contingent earnout consideration (included within interest expense)		153		0
Payments and settlements		(5,900)		0
Purchase price contingent consideration, ending balance	$ 0	$ 0		$ 0		$ 0
[1]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.

Accounting for Derivative Ins71

Accounting for Derivative Instruments - Narrative (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Collateral paid	$ 100,000	$ 0

Accounting for Derivative Ins72

Accounting for Derivative Instruments - Volumetric Underlying Derivative Transactions (Details) MWh in Thousands, MMBTU in Thousands	12 Months Ended
	Dec. 31, 2017MMBTUMWh	Dec. 31, 2016MMBTUMWh
Buy | Non-trading | Natural Gas
Derivatives, Fair Value [Line Items]
Net notional volume	9,191	8,016
Buy | Non-trading | Natural Gas Basis
Derivatives, Fair Value [Line Items]
Net notional volume	0	0
Buy | Non-trading | Electricity
Derivatives, Fair Value [Line Items]
Net notional volume | MWh	8,091	3,958
Buy | Trading | Natural Gas
Derivatives, Fair Value [Line Items]
Net notional volume	26
Sell | Trading | Natural Gas
Derivatives, Fair Value [Line Items]
Net notional volume		953
Sell | Trading | Natural Gas Basis
Derivatives, Fair Value [Line Items]
Net notional volume	225	380

Accounting for Derivative Ins73

Accounting for Derivative Instruments - Gains (Losses) on Derivative Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, net	$ 5,008	$ 22,407	$ (18,497)
Current period settlements on derivatives	16,309	(2,146)	20,547
Non-trading
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, net	5,588	22,254	(18,423)
Current period settlements on derivatives	16,508	(2,284)	20,279
Non-trading | Censtar and Oasis
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, net	100	1,000	3,400
Non-trading | Provider Companies and Major Energy Companies
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, net	500	25,600
Non-trading | Perigee and Other Customers
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, net	1,100
Non-trading | Verde Companies
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, net	1,700
Non-cash Flow Hedging | Non-trading
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, net	5,588	22,254	(18,423)
Current period settlements on derivatives	16,508	(2,284)	20,279
Non-cash Flow Hedging | Trading
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, net	(580)	153	(74)
Current period settlements on derivatives	$ (199)	$ 138	$ 268

Accounting for Derivative Ins74

Accounting for Derivative Instruments - Offsetting Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commodity Contract
Offsetting Assets [Line Items]
Gross Assets	$ 77,140	$ 28,145
Gross Amounts Offset	(42,640)	(16,718)
Net Assets	34,500	11,427
Cash Collateral Offset	0	0
Net Amount Presented	34,500	11,427
Commodity Contract, Current
Offsetting Assets [Line Items]
Gross Assets	61,085	20,271
Gross Amounts Offset	(29,894)	(11,927)
Net Assets	31,191	8,344
Cash Collateral Offset	0	0
Net Amount Presented	31,191	8,344
Non-trading Commodity Contract, Current
Offsetting Assets [Line Items]
Gross Assets	60,167	19,657
Gross Amounts Offset	(29,432)	(11,844)
Net Assets	30,735	7,813
Cash Collateral Offset	0	0
Net Amount Presented	30,735	7,813
Trading Commodity Contract, Current
Offsetting Assets [Line Items]
Gross Assets	918	614
Gross Amounts Offset	(462)	(83)
Net Assets	456	531
Cash Collateral Offset	0	0
Net Amount Presented	456	531
Commodity Contract, Noncurrent
Offsetting Assets [Line Items]
Gross Assets	16,055	7,874
Gross Amounts Offset	(12,746)	(4,791)
Net Assets	3,309	3,083
Cash Collateral Offset	0	0
Net Amount Presented	3,309	3,083
Non-trading Commodity Contract, Noncurrent
Offsetting Assets [Line Items]
Gross Assets	16,055	7,874
Gross Amounts Offset	(12,746)	(4,791)
Net Assets	3,309	3,083
Cash Collateral Offset	0	0
Net Amount Presented	3,309	$ 3,083
Trading Commodity Contract, Noncurrent
Offsetting Assets [Line Items]
Gross Assets	0
Gross Amounts Offset	0
Net Assets	0
Cash Collateral Offset	0
Net Amount Presented	$ 0

Accounting for Derivative Ins75

Accounting for Derivative Instruments - Offsetting Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commodity Contract
Offsetting Liabilities [Line Items]
Gross Liabilities	$ (6,276)	$ (1,059)
Gross Amounts Offset	4,082	311
Net Liabilities	(2,194)	(748)
Cash Collateral Offset	65	0
Net Amount Presented	(2,129)	(748)
Commodity Contract, Current
Offsetting Liabilities [Line Items]
Gross Liabilities	(5,034)	(754)
Gross Amounts Offset	3,332	74
Net Liabilities	(1,702)	(680)
Cash Collateral Offset	65	0
Net Amount Presented	(1,637)	(680)
Non-trading Commodity Contract, Current
Offsetting Liabilities [Line Items]
Gross Liabilities	(4,517)	(662)
Gross Amounts Offset	3,059	69
Net Liabilities	(1,458)	(593)
Cash Collateral Offset	65
Net Amount Presented	(1,393)	(593)
Trading Commodity Contract, Current
Offsetting Liabilities [Line Items]
Gross Liabilities	(517)	(92)
Gross Amounts Offset	273	5
Net Liabilities	(244)	(87)
Cash Collateral Offset	0	0
Net Amount Presented	(244)	(87)
Commodity Contract, Noncurrent
Offsetting Liabilities [Line Items]
Gross Liabilities	(1,242)	(305)
Gross Amounts Offset	750	237
Net Liabilities	(492)	(68)
Cash Collateral Offset	0	0
Net Amount Presented	(492)	(68)
Non-trading Commodity Contract, Noncurrent
Offsetting Liabilities [Line Items]
Gross Liabilities	(676)	(305)
Gross Amounts Offset	732	237
Net Liabilities	56	(68)
Cash Collateral Offset		0
Net Amount Presented	56	$ (68)
Trading Commodity Contract, Noncurrent
Offsetting Liabilities [Line Items]
Gross Liabilities	(566)
Gross Amounts Offset	18
Net Liabilities	(548)
Cash Collateral Offset	0
Net Amount Presented	$ (548)

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of maximum shares available for issuance (in shares)	2,750,000
Stock-based compensation expense	$ 5.1	$ 5.2	$ 3.2
Income tax benefit related to stock-based compensation	$ 2.1	2.1	1.2
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeiture rate of restricted stock units	6.00%
Number of shares vested (in shares)	179,628
Unrecognized compensation expense	$ 7.4
Weighted average period	2 years 10 months 15 days
Restricted Stock Units | General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2.8	2.3	2.2
Restricted Stock Units, Liability Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested (in shares)	176,386
Unrecognized compensation expense	$ 1.8
Weighted average period	2 years 6 months
Other current liabilities related to restricted stock	$ 0.7
Restricted Stock Units, Liability Awards | Other current liabilities
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other current liabilities related to restricted stock		1.5
Restricted Stock Units, Liability Awards | General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2.3	$ 3	$ 1
Non-Employee Director | Restricted Stock Units, Liability Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Officer, Employee, and Employee of Affiliates | Restricted Stock Units | Service Years, Group One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Officer, Employee, and Employee of Affiliates | Restricted Stock Units | Service Years, Group Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Common Class A | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock distributed to the holder of restricted stock units (in shares)	118,514
Number of shares of common stock withheld to cover taxes owed on vested units (in shares)	61,114
Common Class A | Restricted Stock Units, Liability Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock distributed to the holder of restricted stock units (in shares)	123,451
Number of shares of common stock withheld to cover taxes owed on vested units (in shares)	52,935

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Unit Activity (Details)	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Restricted Stock Units
Number of Shares (in thousands)
Balance at beginning of period (in shares) | shares	526,000
Granted (in shares) | shares	307,000
Dividend reinvestment issuances (in shares) | shares	27,000
Vested (in shares) | shares	(179,628)
Forfeited (in shares) | shares	(40,000)
Balance at end of period (in shares) | shares	640,000
Weighted Average Grant Date Fair Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 9.56
Granted (in dollars per share) | $ / shares	18.10
Dividend reinvestment issuances (in dollars per share) | $ / shares	15.64
Vested (in dollars per share) | $ / shares	17.88
Forfeited (in dollars per share) | $ / shares	13.27
Balance at end of period (in dollars per share) | $ / shares	$ 11.56
Restricted Stock Units, Liability Awards
Number of Shares (in thousands)
Balance at beginning of period (in shares) | shares	252,000
Granted (in shares) | shares	140,000
Dividend reinvestment issuances (in shares) | shares	10,000
Vested (in shares) | shares	(176,386)
Forfeited (in shares) | shares	(2,000)
Balance at end of period (in shares) | shares	224,000
Weighted Average Grant Date Fair Value
Balance at beginning of period (in dollars per share) | $ / shares	$ 15.15
Granted (in dollars per share) | $ / shares	12.40
Dividend reinvestment issuances (in dollars per share) | $ / shares	12.40
Vested (in dollars per share) | $ / shares	16.93
Forfeited (in dollars per share) | $ / shares	12.40
Balance at end of period (in dollars per share) | $ / shares	$ 12.40

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Current
Federal	$ 6,992		$ 5,361		$ 268
State	1,952		1,683		(277)
Total Current	8,944		7,044		(9)
Deferred
Federal	26,583		2,944		1,820
State	2,001		438		163
Total Deferred	28,584		3,382		1,983
Provision for income taxes	$ 37,528	[1]	$ 10,426	[2]	$ 1,974	[3]
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)		Jun. 08, 2016	Apr. 01, 2016	Feb. 03, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 01, 2014
Operating Loss Carryforwards [Line Items]
Effective income tax rate					33.00%	13.70%
Statutory federal tax rate					35.00%
Remeasurement of deferred tax balance					$ 13,200,000
Net deferred tax asset					24,185,000	$ 54,109,000
Deferred tax assets					27,341,000	57,506,000
Increase to the liability due to the Tax Receivable Agreement					4,700,000
Increase to deferred tax asset due to the Tax Receivable Agreement					1,800,000
Decrease to equity due to the Tax Receivable Agreement	[1]				2,872,000
Decrease in the Tax Receivable Agreement liability to reflect effect of US Tax Reform					22,300,000
Number of shares of common stock exchanged (in shares)		1,000,000	3,450,000	2,000,000
Income tax penalties and interest expense					0	0	$ 0
Income tax penalties and interest liability					0	0	$ 0
Unrecognized tax benefits					0	0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards					3,800,000
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards					4,100,000
NuDevco
Operating Loss Carryforwards [Line Items]
Net deferred tax asset								$ 15,600,000
NuDevco | Tax Receivable Agreement
Operating Loss Carryforwards [Line Items]
Long-term liability					32,300,000	$ 49,900,000		20,700,000
Deferred tax assets					$ 8,200,000
Long-term deferred tax asset								$ 7,900,000
Retailco | Affiliated Entity
Operating Loss Carryforwards [Line Items]
Long-term liability		$ 6,900,000	$ 10,300,000	$ 10,300,000
Deferred tax assets		$ 2,600,000	$ 3,900,000	$ 3,900,000
Number of shares of common stock exchanged (in shares)		1,000,000	3,450,000	2,000,000
Deferred tax asset as a result of the exchange		$ 5,300,000	$ 7,600,000	$ 8,000,000
[1]	Outstanding shares of common stock, additional paid-in capital and non-controlling interest have been retrospectively adjusted to reflect the two-for-one stock split, which took effect on June 16, 2017. See Note 4 "Equity" for further discussion.

Income Taxes - Income Tax Benef

Income Taxes - Income Tax Benefit Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015	[3]
Income Tax Disclosure [Abstract]
Expected provision at federal statutory rate	$ 39,833		$ 26,635
Increase (decrease) resulting from
Impact of U.S. Tax Reform	13,217		0
Non-controlling interest	(19,810)		(17,740)
State income taxes, net of federal income tax effect	2,569		1,346
Other	1,719		185
Provision for income taxes	$ 37,528	[1]	$ 10,426	[2]	$ 1,974
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets
Investment in Spark HoldCo	$ 18,340	$ 35,359
Benefit of TRA Liability	8,175	19,705
Federal net operating loss carryforward	660	2,076
State net operating loss carryforward	166	366
Total deferred tax assets	27,341	57,506
Deferred Tax Liabilities
Derivative liabilities	(811)	(1,849)
Intangibles	(2,287)	(1,519)
Property and equipment	0	(10)
Other	(58)	(19)
Total deferred tax liabilities	(3,156)	(3,397)
Total deferred tax assets/liabilities	$ 24,185	$ 54,109

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	Jan. 19, 2016USD ($)	Dec. 31, 2017USD ($)claim
Major Energy Companies v. National Gas & Electric, LLC and Spark Energy, Inc.
Loss Contingencies [Line Items]
Number of claims | claim		4
Provider Companies | Pending Litigation | Halifax-American Energy Company, LLC et al v. Provider Power, LLC, Electricity N.H., LLC, Electricity Maine, LLC, Emile Clavet and Kevin Dean
Loss Contingencies [Line Items]
Loss contingency accrual related to indirect tax audits		$ 1
Damages	$ 0.6
Attorney fees	$ 0.3
Indirect Tax Audits
Loss Contingencies [Line Items]
Loss contingency accrual related to indirect tax audits		$ 1.7

Transactions with Affiliates (D

Transactions with Affiliates (Details) - USD ($)

Dec. 27, 2016

Aug. 01, 2016

Jan. 01, 2016

Feb. 28, 2018

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Aug. 23, 2016

Jul. 31, 2015

Jul. 08, 2015

Related Party Transaction [Line Items]

Accounts receivable - affiliates

$ 3,661,000

$ 2,624,000

Accounts payable—affiliates

4,622,000

3,775,000

Asset optimization revenues - affiliates

[2]

(717,000)

[1]

(586,000)

[3]

$ 1,494,000

[4]

Retail cost of revenues (less than in 2015 and 2016)

[5]

552,167,000

[1]

344,944,000

[3]

241,188,000

[4]

General and administrative

[6]

101,127,000

[1]

84,964,000

[3]

61,682,000

[4]

Contributions from NuDevco

0

[7]

0

[8]

129,000

[9]

Adjustments to additional paid-in-capital for the disgorgement of short-swing profits

708,000

1,605,000

Proceeds from disgorgement of stockholders short-swing profits

1,129,000

[7]

941,000

[8]

0

[9]

Subordinated debt—affiliate

0

5,000,000

Long-term portion of note payable

$ 124,801,000

5,000,000

Tax receivable agreement, net cash savings, percentage

15.00%

Convertible Debt | Censtar Convertible Debt | CenStar Earnout

Related Party Transaction [Line Items]

Debt issued

$ 2,100,000

Convertible Debt | Oasis Note | Oasis

Related Party Transaction [Line Items]

Debt issued

$ 5,000,000

Subordinated Debt

Related Party Transaction [Line Items]

Long-term portion of note payable

$ 0

5,000,000

Subordinated Debt | Retailco

Related Party Transaction [Line Items]

Subordinated debt, interest rate

5.00%

Subordinated debt—affiliate

$ 25,000,000

Subordinated debt, advances

$ 1,000,000

Subordinated debt, interest rate on advances

5.00%

Minimum availability under the borrowing base

$ 5,000,000

Affiliated Entity

Related Party Transaction [Line Items]

Cost of revenue - affiliates

53,000

1,633,000

11,285,000

Asset optimization revenues - affiliates

1,334,000

154,000

1,101,000

Retail cost of revenues (less than in 2015 and 2016)

0

9,000

17,000

General and administrative

24,700,000

15,700,000

0

Affiliated Entity | Marlin Transportation Agreement

Related Party Transaction [Line Items]

Retail cost of revenues (less than in 2015 and 2016)

0

100,000

100,000

Affiliated Entity | Allocated Overhead Costs

Related Party Transaction [Line Items]

General and administrative

25,400,000

17,000,000

2,100,000

NuDevco Retail and Retailco LLC

Related Party Transaction [Line Items]

Net capital distributions

15,600,000

23,700,000

15,600,000

Contributions from NuDevco

100,000

NuDevco Retail and Retailco LLC | Payment of Income Taxes Incurred by the Company

Related Party Transaction [Line Items]

Payments of distributions to affiliates

$ 18,200,000

11,300,000

Retailco and NuDevco Retail

Related Party Transaction [Line Items]

Tax receivable agreement, net cash savings, percentage

85.00%

Tax receivable agreement, deferral period (in years)

5 years

Tax receivable agreement, coverage percentage

130.00%

Retailco | Affiliated Entity

Related Party Transaction [Line Items]

Master service agreement term

1 year

Master service agreement renewal term

1 year

Retailco | Affiliated Entity | Allocated Overhead Costs

Related Party Transaction [Line Items]

General and administrative

$ 22,000,000

14,700,000

Retailco | Affiliated Entity | Property and Equipment Capitalized

Related Party Transaction [Line Items]

Capitalized property and equipment

700,000

1,300,000

Retailco and NuDevco Retail | Tax Receivable Agreement

Related Party Transaction [Line Items]

Accounts payable—affiliates

1,400,000

1,400,000

Subsequent Event | Retailco

Related Party Transaction [Line Items]

Proceeds from disgorgement of stockholders short-swing profits

$ 200,000

Additional Paid-In Capital

Related Party Transaction [Line Items]

Adjustments to additional paid-in-capital for the disgorgement of short-swing profits

[10]

708,000

1,605,000

Common Class B

Related Party Transaction [Line Items]

Issuance of Class B common stock to affiliates for Major Energy Companies acquisition

$ 0

[7]

$ 40,000,000

[8]

$ 0

[9]

Share price (in dollars per share)

$ 10

$ 10

Common Class B | Provider Companies

Related Party Transaction [Line Items]

Shares issued (shares)

1,399,484

Issuance of Class B common stock to affiliates for Major Energy Companies acquisition

$ 14,000,000

Common Class A | Retailco and NuDevco Retail

Related Party Transaction [Line Items]

Tax receivable agreement, target dividend (in dollars per share)

$ 0.18125

Series A Preferred Stock | Retailco and NuDevco Retail

Related Party Transaction [Line Items]

Tax receivable agreement, target dividend (in dollars per share)

$ 0.546875

2017 | Retailco

Related Party Transaction [Line Items]

Proceeds from disgorgement of stockholders short-swing profits

$ 500,000

2016 | Retailco

Related Party Transaction [Line Items]

Proceeds from disgorgement of stockholders short-swing profits

$ 700,000

[1]

Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[2]

Net asset optimization revenues includes asset optimization (expense)/revenues—affiliates of $1,334, $154 and $1,101 for the years ended December 31, 2017, 2016 and 2015, respectively, and asset optimization revenues—affiliates cost of revenues of $53, $1,633 and $11,285 for the years ended December 31, 2017, 2016 and 2015, respectively.

[3]

Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[4]

Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[5]

Retail cost of revenues includes retail cost of revenues—affiliates of $0, $9 and $17 for the years December 31, 2017, 2016 and 2015, respectively.

[6]

General and administrative includes general and administrative expense—affiliates of $24,700, $15,700 and $0 for the years ended December 31, 2017, 2016 and 2015, respectively.

[7]

Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[8]

Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[9]

Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.

[10]

Outstanding shares of common stock, additional paid-in capital and non-controlling interest have been retrospectively adjusted to reflect the two-for-one stock split, which took effect on June 16, 2017. See Note 4 "Equity" for further discussion.

Segment Reporting - Narrative (

Segment Reporting - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)supplier	Dec. 31, 2016USD ($)supplier	Dec. 31, 2015USD ($)supplier
Segment Reporting [Abstract]
Asset optimization revenue	$ 178.3	$ 133	$ 154.1
Cost of revenues	$ 179	$ 133.6	$ 152.6
Customer | Retail Electricity
Segment Reporting Information [Line Items]
Number of significant suppliers | supplier	2	2	1

Segment Reporting - Reconciliat

Segment Reporting - Reconciliation (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Reconciliation of Retail Gross Margin to Income before taxes
Income before income tax expense		$ 113,809	[1]	$ 76,099	[2]	$ 27,949	[3]
Change in tax receivable agreement liability		22,267	[1],[4]	0	[2],[5]	0	[3],[6]
Interest and other income		(256)		(957)		(324)
Interest expense		11,134	[1]	8,859	[2]	2,280	[3]
Operating Income		102,420	[1]	84,001	[2]	29,905	[3]
Depreciation and amortization		42,341	[1]	32,788	[2]	25,378	[3]
General and administrative	[7]	101,127	[1]	84,964	[2]	61,682	[3]
Less:
Net asset optimization (expenses) revenue	[8]	(717)	[1]	(586)	[2]	1,494	[3]
Net, Gain (losses) on non-trading derivative instruments		5,008		22,407		(18,497)
Net, Cash settlements on non-trading derivative instruments		16,309		(2,146)		20,547
Retail Gross Margin		224,509		182,369		113,615
Non-trading
Less:
Net, Gain (losses) on non-trading derivative instruments		5,588		22,254		(18,423)
Net, Cash settlements on non-trading derivative instruments		$ 16,508		$ (2,284)		$ 20,279
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[4]	Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[5]	Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[6]	Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.
[7]	General and administrative includes general and administrative expense—affiliates of $24,700, $15,700 and $0 for the years ended December 31, 2017, 2016 and 2015, respectively.
[8]	Net asset optimization revenues includes asset optimization (expense)/revenues—affiliates of $1,334, $154 and $1,101 for the years ended December 31, 2017, 2016 and 2015, respectively, and asset optimization revenues—affiliates cost of revenues of $53, $1,633 and $11,285 for the years ended December 31, 2017, 2016 and 2015, respectively.

Segment Reporting - Financial D

Segment Reporting - Financial Data (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Segment Reporting Information [Line Items]
Total Revenues		$ 798,055	[1]	$ 546,697	[2]	$ 358,153	[3]
Retail cost of revenues	[4]	552,167	[1]	344,944	[2]	241,188	[3]
Less:
Net asset optimization (expense)	[5]	717	[1]	586	[2]	(1,494)	[3]
Net, Gain (losses) on non-trading derivative instruments		5,008		22,407		(18,497)
Current period settlements on non-trading derivatives		16,309		(2,146)		20,547
Retail gross margin		224,509		182,369		113,615
Total Assets		505,949		375,230		162,234
Goodwill		120,154		79,147		18,379		$ 0
Non-trading
Less:
Net, Gain (losses) on non-trading derivative instruments		5,588		22,254		(18,423)
Current period settlements on non-trading derivatives		16,508		(2,284)		20,279
Operating Segments | Retail Electricity
Segment Reporting Information [Line Items]
Total Revenues		657,561		417,229		229,490
Retail cost of revenues		477,012		286,795		170,684
Less:
Net asset optimization (expense)		5		0		0
Retail gross margin		158,468		118,136		60,255
Total Assets		1,228,552		576,757		150,245
Goodwill		117,624		76,617		16,476
Operating Segments | Retail Electricity | Non-trading
Less:
Net, Gain (losses) on non-trading derivative instruments		5,784		17,187		(13,348)
Current period settlements on non-trading derivatives		16,302		(4,889)		11,899
Operating Segments | Retail Natural Gas
Segment Reporting Information [Line Items]
Total Revenues		140,494		129,468		128,663
Retail cost of revenues		75,155		58,149		70,504
Less:
Net asset optimization (expense)		712		586		(1,494)
Retail gross margin		66,041		64,233		53,360
Total Assets		421,896		242,739		113,583
Goodwill		2,530		2,530		1,903
Operating Segments | Retail Natural Gas | Non-trading
Less:
Net, Gain (losses) on non-trading derivative instruments		(196)		5,067		(5,075)
Current period settlements on non-trading derivatives		206		2,605		8,380
Corporate and Other
Segment Reporting Information [Line Items]
Total Revenues		0		0		0
Retail cost of revenues		0		0		0
Less:
Net asset optimization (expense)		0		0		0
Retail gross margin		0		0		0
Total Assets		209,428		169,404		88,823
Goodwill		0		0		0
Corporate and Other | Non-trading
Less:
Net, Gain (losses) on non-trading derivative instruments		0		0		0
Current period settlements on non-trading derivatives		0		0		0
Eliminations
Segment Reporting Information [Line Items]
Total Revenues		0		0		0
Retail cost of revenues		0		0		0
Less:
Net asset optimization (expense)		0		0		0
Retail gross margin		0		0		0
Total Assets		(1,353,927)		(613,670)		(190,417)
Goodwill		0		0		0
Eliminations | Non-trading
Less:
Net, Gain (losses) on non-trading derivative instruments		0		0		0
Current period settlements on non-trading derivatives		$ 0		$ 0		$ 0
[1]	Financial information includes results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[2]	Financial information includes results attributable to the acquisition of Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[3]	Financial information includes results attributable to the acquisition of Oasis Power Holdings LLC from an affiliate on May 12, 2015. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.
[4]	Retail cost of revenues includes retail cost of revenues—affiliates of $0, $9 and $17 for the years December 31, 2017, 2016 and 2015, respectively.
[5]	Net asset optimization revenues includes asset optimization (expense)/revenues—affiliates of $1,334, $154 and $1,101 for the years ended December 31, 2017, 2016 and 2015, respectively, and asset optimization revenues—affiliates cost of revenues of $53, $1,633 and $11,285 for the years ended December 31, 2017, 2016 and 2015, respectively.

Customer Acquisitions (Details)

Customer Acquisitions (Details) - Customer Relationships kWh in Thousands, $ in Millions	Apr. 03, 2017USD ($)kWh	Mar. 31, 2015USD ($)kWh
Northern California
Finite-Lived Intangible Assets [Line Items]
Residential and commercial natural gas contracts (in kwh) | kWh		95,000
Contract purchase price | $		$ 2
Amortization period		3 years
Perigee
Finite-Lived Intangible Assets [Line Items]
Residential and commercial natural gas contracts (in kwh) | kWh	440,000
Contract purchase price | $	$ 7.5

Equity Method Investment (Detai

Equity Method Investment (Details) - eREX Spark ¥ in Millions, $ in Millions	1 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)	Sep. 30, 2015JPY (¥)	Dec. 31, 2017USD ($)director
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investment	$ 1.4	¥ 156.4
Ownership percentage			20.00%
Dividends distributed percentage			30.00%
Number of years dividend is paid thereafter			4 years
Number of Board of Directors | director			4
Number of Board of Directors appointed by the company | director			1
Board of Director members' percentage			25.00%
Equity method investment | $			$ 2.5
Share in equity method investment earnings | $			$ 0.2

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, kWh in Thousands

Mar. 07, 2018USD ($)usd_per_rcekWhstatemarket

Mar. 01, 2018USD ($)kWhstatemarket

Jan. 26, 2018USD ($)shares

Jan. 18, 2018USD ($)$ / shares

Mar. 15, 2017USD ($)

Mar. 09, 2018USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

[3]

Jan. 23, 2018USD ($)

Jan. 12, 2018USD ($)

Jan. 11, 2018USD ($)

Subsequent Event [Line Items]

Promissory note payable

$ 145,744,000

$ 78,370,000

Dividends declared

3,038,000

Net proceeds from offering

$ 39,000,000

40,241,000

[1]

$ 0

[2]

$ 0

Subsequent Event

Subsequent Event [Line Items]

Net proceeds from offering

$ 48,900,000

$ 48,900,000

Common Class A | Subsequent Event

Subsequent Event [Line Items]

Dividends declared (in dollars per share) | $ / shares

$ 0.18125

Series A Preferred Stock

Subsequent Event [Line Items]

Dividends declared

2,100,000

Series A Preferred Stock | Subsequent Event

Subsequent Event [Line Items]

Dividends declared (in dollars per share) | $ / shares

0.546875

Annualized dividend (in dollars per share) | $ / shares

$ 2.1875

Aggregate shares sold in offering (in shares) | shares

2,000,000

Series A Preferred Stock | Subsequent Event | Scenario, Forecast

Subsequent Event [Line Items]

Dividends declared

$ 8,100,000

HIKO Energy, LLC | Subsequent Event

Subsequent Event [Line Items]

Purchase price

$ 6,000,000

Number of markets | market

42

Number of states | state

7

Major Energy Companies | Subsequent Event

Subsequent Event [Line Items]

Purchase price

$ 12,500,000

Number of markets | market

24

Number of states | state

8

RCE cash purchase price (in usd per rce) | usd_per_rce

250

Notes Payable | Verde Earnout Termination Note

Subsequent Event [Line Items]

Promissory note payable

$ 5,900,000

Notes Payable | Verde Earnout Termination Note | Subsequent Event

Subsequent Event [Line Items]

Promissory note payable

$ 5,900,000

Senior Credit Facility | Subsequent Event

Subsequent Event [Line Items]

Line of credit facility, maximum borrowing capacity

$ 200,000,000

$ 150,000,000

Customer Relationships | HIKO Energy, LLC | Subsequent Event

Subsequent Event [Line Items]

Residential customer equivalents (in kwh) | kWh

290,000

Customer Relationships | Major Energy Companies | Subsequent Event

Subsequent Event [Line Items]

Residential customer equivalents (in kwh) | kWh

500,000

[1]

Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[2]

Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies from an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[3]

Financial information has been recast to include results attributable to the acquisition of Oasis Power Holdings LLC by an affiliate on May 12, 2015. See Note 2 "Basis of Presentation and Summary of Significant Accounting Policies" for further discussion.