| Cover Document | Mar. 03, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 3, 2021 |
| Entity Registrant Name | Spark Energy, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36559 |
| Entity Tax Identification Number | 46-5453215 |
| Entity Address, Address Line One | 12140 Wickchester Ln |
| Entity Address, Address Line Two | Suite 100 |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77079 |
| City Area Code | 713 |
| Local Phone Number | 600-2600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001606268 |
| Amendment Flag | false |
| Class A common stock, par value $0.01 per share | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Class A common stock, par value $0.01 per share |
| Trading Symbol | SPKE |
| Security Exchange Name | NASDAQ |
| 8.75% Series A Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Stock, par value $0.01 per share | |
| Document Information [Line Items] | |
| Title of 12(b) Security | 8.75% Series A Fixed-to-Floating RateCumulative Redeemable Perpetual Preferred Stock, par value $0.01 per share |
| Trading Symbol | SPKEP |
| Security Exchange Name | NASDAQ |
