Contracts Accounted for as Financial Guaranty Insurance - Reconciliation of Net Expected Loss to be Paid and Expensed (Details) - USD ($) $ in Millions |
Mar. 31, 2026 |
Dec. 31, 2025 |
Mar. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|---|---|
| Guarantor Obligations [Line Items] | ||||
| Net expected loss to be paid (recovered) - FG insurance | $ 141 | $ 101 | $ 150 | $ 106 |
| Net expected loss to be expensed (present value) | 275 | |||
| Financial Guarantee Insurance And Other Product Line | ||||
| Guarantor Obligations [Line Items] | ||||
| Net expected loss to be paid (recovered) - FG insurance | 129 | |||
| Contra-paid, net | 22 | |||
| Salvage and subrogation recoverable, net | 433 | |||
| Loss and LAE reserve - FG insurance contracts, net of reinsurance | (309) | |||
| Net expected loss to be expensed (present value) | $ 275 |