Claim and Claim Adjustment Expense Reserves (Specialty - Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development) (Details) - Specialty - 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] | ||||
| Medical Professional Liability | $ 0 | $ (2) | $ 0 | $ (2) |
| Other Professional Liability and Management Liability | 18 | 17 | 18 | 17 |
| Surety | (22) | (8) | (22) | (26) |
| Warranty | 0 | 0 | 10 | 13 |
| Other | 4 | (10) | 4 | (10) |
| Total pretax (favorable) unfavorable development | $ 0 | $ (3) | $ 10 | $ (8) |