Liability for Future Policyholder Benefits - Changes in Deferred Profit Liability (Details) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Deferred Profit Liability [Roll Forward] | ||
| Balance, beginning of period | $ 481.7 | $ 412.1 |
| Profits deferred | 77.0 | 79.6 |
| Interest accrual | 11.2 | 9.7 |
| Amortization | (58.9) | (57.6) |
| Effect of actual variances from expected experience and other changes | (0.7) | 0.7 |
| Balance, end of period | $ 510.3 | $ 444.5 |