Financial Risk Management - Credit Risk - Reinsurance contract assets (Details) - USD ($) $ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Financial Risk Management | ||
| Capital and surplus requirement | $ 500.0 | |
| Funds available for collateralization | 800.0 | |
| Reinsurance contract assets held | $ 11,251.0 | $ 10,682.6 |
| A.M. Best rating A- or higher | ||
| Financial Risk Management | ||
| Reinsurance exposure percentage | 91.00% | 88.00% |
| Pools and associations | ||
| Financial Risk Management | ||
| Reinsurance exposure percentage | 9.00% | 12.00% |