| Document and Entity Information | Mar. 24, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001801754 |
| Document Type | 8-K |
| Document Period End Date | Mar. 24, 2021 |
| Entity Registrant Name | TREAN INSURANCE GROUP, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-39392 |
| Entity Tax Identification Number | 84-4512647 |
| Entity Address, Address Line One | 150 Lake Street West |
| Entity Address, City or Town | Wayzata |
| Entity Address, State or Province | MN |
| Entity Address, Postal Zip Code | 55391 |
| City Area Code | (952) |
| Local Phone Number | 974-2200 |
| 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 |
| Trading Symbol | TIG |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
