| Document and Entity Information Document | Nov. 05, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 1, 2021 |
| Entity Registrant Name | ProAssurance Corporation |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-16533 |
| Entity Tax Identification Number | 63-1261433 |
| Entity Central Index Key | 0001127703 |
| Amendment Flag | false |
| Entity Address, Address Line One | 100 Brookwood Place, |
| Entity Address, City or Town | Birmingham, |
| Entity Address, State or Province | AL |
| Entity Address, Postal Zip Code | 35209 |
| City Area Code | (205) |
| Local Phone Number | 877-4400 |
| 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 $0.01 per share |
| Trading Symbol | PRA |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
