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 | |
|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Liability for Claims and Claims Adjustment Expense [Line Items] | ||
| Medical Professional Liability | $ 0 | $ 0 |
| Other Professional Liability and Management Liability | 0 | 0 |
| Surety | 0 | (18) |
| Warranty | 10 | 13 |
| Other | 0 | 0 |
| Total pretax (favorable) unfavorable development | $ 10 | $ (5) |