Derivatives - Counterparty collateral (Details) - USD ($) $ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Cash | Collateral deposits on derivative contracts for the benefit of the company | ||
| Derivatives | ||
| Financial assets pledged as collateral | $ 51.5 | $ 50.0 |
| Government securities | ||
| Derivatives | ||
| Financial assets pledged as collateral | 1,919.2 | 1,015.1 |
| Government securities | Collateral deposits on derivative contracts for the benefit of the company | ||
| Derivatives | ||
| Financial assets pledged as collateral | 1,919.2 | 1,015.1 |
| Holding company cash and investments | Collateral deposits on derivative contracts for the benefit of the derivative counterparties | ||
| Derivatives | ||
| Financial assets pledged as collateral | 398.6 | 344.4 |
| Amount of collateral originally required for deposit | 378.1 | 271.6 |
| Amount of collateral deposits attributable to changes in fair value since the most recent reset date | $ 20.5 | $ 72.8 |