Investments - Holding gains (losses) on equity securities still held (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Holding Gains (Losses) on Equity Securities Still Held [Line Items] | ||||
| Holding gains (losses) on equity securities | $ 11 | $ 6 | $ 19 | $ 42 |
| Realized gains (losses) on securities | ||||
| Holding Gains (Losses) on Equity Securities Still Held [Line Items] | ||||
| Holding gains (losses) on equity securities | 9 | (3) | 16 | 17 |
| Net investment income | ||||
| Holding Gains (Losses) on Equity Securities Still Held [Line Items] | ||||
| Holding gains (losses) on equity securities | $ 2 | $ 9 | $ 3 | $ 25 |