Claim and Claim Adjustment Expense Reserves (Net Prior Year Development) (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Segment Reporting Information [Line Items] | ||
| Pretax (favorable) unfavorable premium development, excluding Life & Group | $ 83 | $ (7) |
| Specialty | Property and Casualty Segments | ||
| Segment Reporting Information [Line Items] | ||
| Pretax (favorable) unfavorable premium development, excluding Life & Group | 10 | (5) |
| Commercial | Property and Casualty Segments | ||
| Segment Reporting Information [Line Items] | ||
| Pretax (favorable) unfavorable premium development, excluding Life & Group | 51 | (2) |
| International | Property and Casualty Segments | ||
| Segment Reporting Information [Line Items] | ||
| Pretax (favorable) unfavorable premium development, excluding Life & Group | 0 | 0 |
| Corporate & Other | ||
| Segment Reporting Information [Line Items] | ||
| Pretax (favorable) unfavorable premium development, excluding Life & Group | $ 22 | $ 0 |