Investments - Schedule of Net Realized and Unrealized Gains on Investments (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Investments, Debt and Equity Securities [Abstract] | ||||
| Net realized (losses) gains on fixed maturity and short-term investments | $ (1.1) | $ 0.3 | $ (1.0) | $ 0.6 |
| Net realized gains on equity method investments | 0.0 | 0.1 | 0.0 | 2.1 |
| Net realized gains on other investments | 27.1 | 0.0 | 27.1 | 0.0 |
| Net realized gains on investments | 26.0 | 0.4 | 26.1 | 2.7 |
| Net unrealized gains (losses) on other investments | 27.0 | (0.5) | 27.0 | 1.2 |
| Net realized and unrealized gains (losses) on investments | $ 53.0 | $ (0.1) | $ 53.1 | $ 3.9 |