Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Total assets	$ 18,208	$ 15,334
Total liabilities	11,708	8,629
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total assets	260	296
Variable Interest Entity, Primary Beneficiary | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	269	316
Variable Interest Entity, Primary Beneficiary | Nonrecourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	20	17
U.S. | First Lien | RMBS | Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total assets	221	243
U.S. | First Lien | RMBS | Variable Interest Entity, Primary Beneficiary | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	227	260
U.S. | First Lien | RMBS | Variable Interest Entity, Primary Beneficiary | Nonrecourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	20	17
U.S. | Second Lien | RMBS | Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total assets	39	53
U.S. | Second Lien | RMBS | Variable Interest Entity, Primary Beneficiary | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	$ 42	$ 56