| Document and Entity Information | Apr. 29, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | AMERISAFE INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001018979 |
| Document Type | 8-K |
| Document Period End Date | Apr. 29, 2021 |
| Entity Incorporation State Country Code | TX |
| Entity File Number | 001-12251 |
| Entity Tax Identification Number | 75-2069407 |
| Entity Address, Address Line One | 2301 Highway 190 West |
| Entity Address, City or Town | DeRidder |
| Entity Address, State or Province | LA |
| Entity Address, Postal Zip Code | 70634 |
| City Area Code | (337) |
| Local Phone Number | 463-9052 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.01 per share |
| Trading Symbol | AMSF |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
