Fair Value Measurements - Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance for Residential Mortgage Loans Measured at Fair Value (Details) - Residential mortgage loans - USD ($) $ in Millions |
Mar. 31, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Aggregate Fair Value | ||
| Residential mortgage loans measured at fair value | $ 819 | $ 764 |
| Past due loans of 30-89 days | 1 | 2 |
| Past due loans of 90 days or more | 1 | |
| Nonaccrual loans | 4 | 4 |
| Aggregate Unpaid Principal Balance | ||
| Residential mortgage loans measured at fair value | 822 | 758 |
| Past due loans of 30-89 days | 1 | 2 |
| Past due loans of 90 days or more | 1 | |
| Nonaccrual loans | $ 4 | $ 4 |