| Cover | Jan. 04, 2021 |
| Cover [Abstract] | |
| Document Period End Date | Jan. 4, 2021 |
| Document Type | 8-K |
| Entity Registrant Name | JEFFERIES FINANCIAL GROUP INC. |
| Entity File Number | 1-5721 |
| Entity Incorporation, State or Country Code | NY |
| Entity Tax Identification Number | 13-2615557 |
| Entity Address, Address Line One | 520 Madison Avenue |
| Entity Address, City or Town | New York, |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10022 |
| City Area Code | 212 |
| Local Phone Number | 460-1900 |
| 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 $1.00 Per Share |
| Trading Symbol | JEF |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000096223 |
| Amendment Flag | false |
