Investments - Net Investment Losses (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Gain (Loss) on Securities [Line Items] | ||||
| Net investment gains (losses) | $ (0.1) | $ (5.9) | $ (2.3) | $ (9.2) |
| Fixed maturity securities | ||||
| Gain (Loss) on Securities [Line Items] | ||||
| Net investment gains (losses) | (0.1) | (4.1) | 0.4 | (3.9) |
| Equity securities | ||||
| Gain (Loss) on Securities [Line Items] | ||||
| Net investment gains (losses) | (0.3) | (0.7) | (1.6) | (2.0) |
| Short-term investments and other | ||||
| Gain (Loss) on Securities [Line Items] | ||||
| Net investment gains (losses) | $ 0.3 | $ (1.1) | $ (1.1) | $ (3.3) |