Equity - Basic and Diluted Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity [Abstract]
Net income (loss) attributable to Spark Energy, Inc. stockholders	$ 11,159	$ (7,115)	$ 15,638	$ (6,333)
Less: Dividends on Series A preferred stock	2,039	2,027	3,539	4,054
Net income (loss) attributable to stockholders of Class A common stock	$ 9,120	$ (9,142)	$ 12,099	$ (10,387)
Basic weighted average Class A common shares outstanding (in shares)	14,558	14,246	14,469	14,191
Basic income (loss) per share attributable to stockholders (in dollars per share)	$ 630	$ (0.64)	$ 840	$ (0.73)
Net income (loss) attributable to stockholders of Class A common stock	$ 9,120	$ (9,142)	$ 12,099	$ (10,387)
Effect of conversion of Class B common stock to shares of Class A common stock	0	(16,557)	0	(15,242)
Diluted net income (loss) attributable to stockholders of Class A common stock	$ 9,120	$ (25,699)	$ 12,099	$ (25,629)
Basic weighted average Class A common shares outstanding (in shares)	14,558	14,246	14,469	14,191
Effect of dilutive Class B common stock (in shares)	0	20,800	0	20,800
Effect of dilutive restricted stock units (in shares)	205	0	100	0
Diluted weighted average shares outstanding (in shares)	14,763	35,046	14,569	34,991
Diluted income (loss) per share attributable to stockholders (in dollars per share)	$ 620	$ (0.73)	$ 830	$ (0.73)