Fair Value Measurements - Transfers (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Fair Value Hierarchy Levels Transfers | ||||
| Transfers out of Level 3 into Level 2, net derivative assets (liabilities) | $ 0.1 | |||
| Fixed maturities, trading | ||||
| Fair Value Hierarchy Levels Transfers | ||||
| Transfers out of Level 3 into Level 2 | $ 4.8 | |||
| Available-for-sale | Fixed maturities | ||||
| Fair Value Hierarchy Levels Transfers | ||||
| Transfers out of Level 2 into Level 3 | $ 32.6 | 121.5 | $ 85.2 | 121.5 |
| Transfers out of Level 3 into Level 2 | 112.9 | 117.7 | 24.8 | |
| Available-for-sale | States and political subdivisions | ||||
| Fair Value Hierarchy Levels Transfers | ||||
| Transfers out of Level 2 into Level 3 | 32.6 | 32.6 | ||
| Available-for-sale | Other debt obligations | ||||
| Fair Value Hierarchy Levels Transfers | ||||
| Transfers out of Level 2 into Level 3 | $ 121.5 | 52.6 | 121.5 | |
| Transfers out of Level 3 into Level 2 | $ 112.9 | $ 117.7 | $ 24.8 | |