| Cover | Jan. 13, 2021 |
| Schedule of Capitalization, Equity [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jan. 13, 2021 |
| Entity File Number | 1-35327 |
| Entity Registrant Name | GENIE ENERGY LTD. |
| Entity Central Index Key | 0001528356 |
| Entity Tax Identification Number | 45-2069276 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 520 Broad Street |
| Entity Address, City or Town | Newark |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 07102 |
| City Area Code | (973) |
| Local Phone Number | 438-3500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Class B common stock, par value $.01 per share | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Class B common stock, par value $.01 per share |
| Trading Symbol | GNE |
| Security Exchange Name | NYSE |
| Series 2012-A Preferred stock, par value $.01 per share | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Series 2012-A Preferred stock, par value $.01 per share |
| Trading Symbol | GNE PRA |
| Security Exchange Name | NYSE |
