| Cover Page | Nov. 19, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 19, 2021 |
| Entity Registrant Name | OLD REPUBLIC INTERNATIONAL CORPORATION |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-10607 |
| Entity Central Index Key | 0000074260 |
| Amendment Flag | false |
| Current Fiscal Year End Date | --12-31 |
| Entity Tax Identification Number | 36-2678171 |
| Entity Address, Address Line One | 307 North Michigan Avenue |
| Entity Address, City or Town | Chicago |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60601 |
| City Area Code | (312) |
| Local Phone Number | 346-8100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock / $1 par value |
| Trading Symbol | ORI |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
