| Cover | Jan. 20, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jan. 20, 2021 |
| Entity File Number | 001-37503 |
| Entity Registrant Name | B. Riley Financial, Inc. |
| Entity Central Index Key | 0001464790 |
| Entity Tax Identification Number | 27-0223495 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 11100 Santa Monica Boulevard |
| Entity Address, Address Line Two | Suite 800 |
| Entity Address, City or Town | Los Angeles |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 90025 |
| City Area Code | 310 |
| Local Phone Number | 966-1444 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| Trading Symbol | RILY |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Information, Former Legal or Registered Name | Not Applicable |
