Investments - Fair Value Changes to Equity Securities (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 gains (losses) recognized on equity securities | $ 2.7 | $ (1.1) | $ 0.0 | $ 1.7 |
| Less: Net realized gains (losses) related to sales of equity securities | 0.0 | (13.5) | 0.0 | (14.0) |
| Total fair value changes to equity securities held | $ 2.7 | $ 12.4 | $ 0.0 | $ 15.7 |