Claim and Claim Adjustment Expense Reserves (Commercial - Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development) (Details) - Commercial - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||||
| Commercial | $ 0 | $ 21 | $ 50 | $ 21 |
| General Liability | 62 | 19 | 62 | 19 |
| Workers' Compensation | (66) | (47) | (65) | (49) |
| Property and Other | 0 | 1 | 0 | 1 |
| Total pretax (favorable) unfavorable development | $ (4) | $ (6) | $ 47 | $ (8) |