Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 04, 2020
Class of Stock [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Registrant Name	Spark Energy, Inc.
Entity Central Index Key	0001606268
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Class A Common Stock
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		14,509,380
Class B Common Stock
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		20,800,000