Investments - Gross Realized Gains and Gross Realized Losses from Sales or Maturities of Available for Sale Securities (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Investments, Debt and Equity Securities [Abstract] | ||||
| Aggregate fair value of available for sale securities sold | $ 2,700 | $ 2,600 | $ 6,500 | $ 7,400 |
| Gross Realized Gains | 18 | 14 | 38 | 30 |
| Gross Realized Losses | $ 81 | $ 165 | $ 231 | $ 443 |