Document and Entity Information Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Feb. 28, 2017	Jun. 30, 2016
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Trading Symbol	SPKE
Entity Registrant Name	Spark Energy, Inc.
Entity Central Index Key	0001606268
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Class of Stock [Line Items]
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 195.0
Common Class A
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		6,496,559
Common Class B
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		10,742,563