| DEI Document | Oct. 28, 2021 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 28, 2021 |
| Entity Registrant Name | KINSALE CAPITAL GROUP, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-37848 |
| Entity Tax Identification Number | 98-0664337 |
| Entity Address, Address Line One | 2035 Maywill Street |
| Entity Address, Address Line Two | Suite 100 |
| Entity Address, City or Town | Richmond |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 23230 |
| City Area Code | 804 |
| Local Phone Number | 289-1300 |
| 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 |
| Trading Symbol | KNSL |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001669162 |
