Equity - Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	7 Months Ended	12 Months Ended
	Jul. 31, 2014	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to stockholders of Class A common stock	$ (21)	$ 14,444	[1]	$ 3,865	[2]	$ (54)
Basic weighted average Class A common shares outstanding (in shares)		5,701	[1]	3,064	[2]	3,000
Basic EPS attributable to Spark Energy, Inc. stockholders (in dollars per share)		$ 2.53	[1]	$ 1.26	[2]	$ (0.02)
Effect of conversion of Class B common stock to shares of Class A common stock		$ 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		(310)		(334)
Diluted net income attributable to stockholders of Class A common stock		$ 14,134		$ 3,531
Basic weighted average Class A common shares outstanding (in shares)		5,701	[1]	3,064	[2]	3,000
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)		505		210
Effect of dilutive restricted stock units (in shares)		139		53
Diluted weighted average shares outstanding (in shares)		6,345	[1]	3,327	[2]	3,000
Diluted EPS attributable to Spark Energy, Inc. stockholders (in dollars per share)		$ 2.23	[1]	$ 1.06	[2]	$ (0.02)
Common Class A
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic weighted average Class A common shares outstanding (in shares)		5,701		3,064
Basic weighted average Class A common shares outstanding (in shares)		5,701		3,064
Common Class B
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive Class B common stock (in shares)		0		0

[1] Financial information has been recast to include results attributable to the acquisition of Major Energy Companies by 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.

[2] (2) Financial information has been recast to include 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.