Investments - Securities Posted as Collateral (Details) - USD ($) $ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Securities Posted as Collateral | ||
| Mortgage loans | $ 21,092.7 | $ 21,008.3 |
| Pledged as collateral | ||
| Securities Posted as Collateral | ||
| Fixed maturities available-for-sale and trading securities posted as collateral for a reinsurance arrangement, derivative credit support annex (collateral) agreements, Futures Commission Merchant agreements, a lending arrangement and an obligation under funding agreements with Federal Home Loan Bank of Des Moines | 3,658.6 | 3,610.4 |
| Pledged as collateral | Funding agreements with Federal Home Loan Bank | ||
| Securities Posted as Collateral | ||
| Mortgage loans | 6,630.7 | 6,587.5 |
| Pledged as collateral with right to be sold or repledged | ||
| Securities Posted as Collateral | ||
| Securities posted as collateral eligible to be sold or repledged | $ 603.7 | $ 485.0 |