| Cover | Dec. 31, 2020 |
| Schedule of Capitalization, Equity [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 31, 2020 |
| 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 Blvd |
| 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 |
| Entity Emerging Growth Company | false |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Common Stock, par value $0.0001 per share | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| Trading Symbol | RILY |
| Security Exchange Name | NASDAQ |
| Depositary Shares (each representing a 1/1000 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Depositary Shares (each representing a 1/1000 |
| Trading Symbol | RILYP |
| Security Exchange Name | NASDAQ |
| Depositary Shares (each representing a 1/1000th interest in a 7.375% Series B Cumulative Perpetual Preferred Share, par value $0.0001 per share) | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | Depositary Shares (each representing a 1/1000th interest in a 7.375% Series B Cumulative Perpetual Preferred Share, par value $0.0001 per share) |
| Trading Symbol | RILYL |
| Security Exchange Name | NASDAQ |
| 7.25% Senior Notes due 2027 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 7.25% Senior Notes due 2027 |
| Trading Symbol | RILYG |
| Security Exchange Name | NASDAQ |
| 7.50% Senior Notes due 2027 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 7.50% Senior Notes due 2027 |
| Trading Symbol | RILYZ |
| Security Exchange Name | NASDAQ |
| 7.375% Senior Notes due 2023 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 7.375% Senior Notes due 2023 |
| Trading Symbol | RILYH |
| Security Exchange Name | NASDAQ |
| 6.875% Senior Notes due 2023 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 6.875% Senior Notes due 2023 |
| Trading Symbol | RILYI |
| Security Exchange Name | NASDAQ |
| 6.75% Senior Notes due 2024 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 6.75% Senior Notes due 2024 |
| Trading Symbol | RILYO |
| Security Exchange Name | NASDAQ |
| 6.50% Senior Notes due 2026 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 6.50% Senior Notes due 2026 |
| Trading Symbol | RILYN |
| Security Exchange Name | NASDAQ |
| 6.375% Senior Notes due 2025 | |
| Schedule of Capitalization, Equity [Line Items] | |
| Title of 12(b) Security | 6.375% Senior Notes due 2025 |
| Trading Symbol | RILYM |
| Security Exchange Name | NASDAQ |
