Statutory Requirements and Dividends Restrictions - Summary of Statutory Requirements and Dividends Restrictions (Details) - USD ($) $ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| United States: | ||
| Statutory Requirements and Dividend Restrictions [Line Items] | ||
| Required statutory capital and surplus | $ 579.3 | $ 565.7 |
| Actual statutory capital and surplus | 1,202.3 | 1,164.9 |
| Bermuda | ||
| Statutory Requirements and Dividend Restrictions [Line Items] | ||
| Required statutory capital and surplus | 595.3 | 579.3 |
| Actual statutory capital and surplus | 1,550.0 | 1,761.3 |
| United Kingdom: | ||
| Statutory Requirements and Dividend Restrictions [Line Items] | ||
| Required statutory capital and surplus | 270.4 | 277.3 |
| Actual statutory capital and surplus | $ 611.7 | $ 651.0 |