Contracts Accounted for as Financial Guaranty Insurance - Gross Premium Receivable Net of Commissions on Assumed Business Roll Forward (Details) - USD ($) $ in Millions |
9 Months Ended | |
|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Gross Premium Receivable Net of Ceding Commissions [Roll Forward] | ||
| Beginning of year | $ 1,572 | $ 1,551 |
| Less: Specialty insurance premium receivable | 2 | 1 |
| Financial guaranty insurance premiums receivable | 1,570 | 1,550 |
| New business and supplemental premiums, net of commissions | 275 | 214 |
| Gross premiums received, net of commissions | (299) | (265) |
| Adjustments: | ||
| Changes in the expected term and debt service assumptions | (2) | (23) |
| Accretion of discount, net of commissions on assumed business | 22 | 26 |
| Foreign exchange gain (loss) on remeasurement | (23) | 81 |
| Change in allowance for credit losses | (3) | (1) |
| Financial guaranty insurance premiums receivable | 1,540 | 1,582 |
| Specialty insurance premium receivable | 2 | 1 |
| Ending balance | $ 1,542 | $ 1,583 |