| Document and Entity Information | Oct. 15, 2019 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0000096223 |
| Document Type | 8-K |
| Document Period End Date | Oct. 15, 2019 |
| Entity Registrant Name | Jefferies Financial Group Inc. |
| Entity Incorporation State Country Code | NY |
| Entity File Number | 1-05721 |
| Entity Tax Identification Number | 13-2615557 |
| Entity Address, Address Line One | 520 Madison Ave. |
| 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 |
| Security 12b Title | Common Stock, Par Value $1.00 Per Share |
| Trading Symbol | JEF |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
