Equity - Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended
		Jan. 08, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Class of Stock [Line Items]
Net income attributable to Spark Energy, Inc. stockholders	[1],[2]		$ 1,079	$ 2,341	$ 3,349	$ 6,514
Less: Accumulated dividend on Series A preferred stock			991	0	1,174	0
Net income attributable to stockholders of Class A common stock			$ 88	$ 2,341	$ 2,175	$ 6,514
Basic weighted average Class A common shares outstanding			13,104,000	12,086,000	13,050,000	9,799,000
Basic EPS attributable to shareholders (in dollars per share)			$ 0.01	$ 0.19	$ 0.17	$ 0.66
Effect of conversion of Class B common stock to shares of Class A common stock			$ 0	$ 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 (1)			0	(332)	0	(312)
Diluted net income attributable to stockholders of Class A common stock			$ 88	$ 2,009	$ 2,175	$ 6,202
Basic weighted average Class A common shares outstanding			13,104,000	12,086,000	13,050,000	9,799,000
Effect of dilutive Class B common stock (in shares)			0	0	0	0
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			0	986,000	0	986,000
Effect of dilutive restricted stock units (in shares)			272,000	206,000	207,000	174,000
Diluted weighted average shares outstanding			13,376,000	13,278,000	13,257,000	10,959,000
Diluted EPS attributable to shareholders (in dollars per share)			$ 0.01	$ 0.15	$ 0.16	$ 0.57
CenStar Note | Common Class B
Class of Stock [Line Items]
Number of shares from conversion (shares)		269,462

[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" for further discussion.

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