Contracts Accounted for as Insurance - Reconciliation of Net Expected Loss to be Paid and Expensed (Details) - USD ($) $ in Millions |
Jun. 30, 2025 |
Mar. 31, 2025 |
Dec. 31, 2024 |
Jun. 30, 2024 |
Mar. 31, 2024 |
Dec. 31, 2023 |
|---|---|---|---|---|---|---|
| Guarantor Obligations [Line Items] | ||||||
| Net expected loss to be paid (recovered) - financial guaranty insurance | $ 186 | $ 150 | $ 106 | $ 447 | $ 433 | $ 505 |
| Net expected loss to be expensed (present value) | 260 | |||||
| Financial Guarantee Insurance And Other Product Line | ||||||
| Guarantor Obligations [Line Items] | ||||||
| Net expected loss to be paid (recovered) - financial guaranty insurance | 170 | |||||
| Contra-paid, net | 23 | |||||
| Salvage and subrogation recoverable, net | 380 | |||||
| Loss and LAE reserve - financial guaranty insurance contracts, net of reinsurance | (313) | |||||
| Net expected loss to be expensed (present value) | $ 260 |