Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2015	Nov. 10, 2015
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Trading Symbol	SPKE
Entity Registrant Name	Spark Energy, Inc.
Entity Central Index Key	0001606268
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Common Class A
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		3,097,193
Common Class B
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		10,750,000