Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Total assets	$ 16,843	$ 18,208
Total liabilities	11,551	11,708
Cash	107	120	$ 162
Variable Interest Entity, Primary Beneficiary | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	702	269
Variable Interest Entity, Primary Beneficiary | Nonrecourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	13	20
Variable Interest Entity, Primary Beneficiary | RMBS | U.S. | First Lien | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	176	227
Variable Interest Entity, Primary Beneficiary | RMBS | U.S. | First Lien | Nonrecourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	13	20
Variable Interest Entity, Primary Beneficiary | RMBS | U.S. | Second Lien | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	24	42
Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	495	0
Variable Interest Entity, Primary Beneficiary | Other | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	7	0
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total assets	416	260
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | RMBS | U.S. | First Lien
Variable Interest Entity [Line Items]
Total assets	167	221
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | RMBS | U.S. | Second Lien
Variable Interest Entity [Line Items]
Total assets	30	39
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | Puerto Rico Trusts
Variable Interest Entity [Line Items]
Total assets	212	0
Asset, fair value	209
Cash	2
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | Other
Variable Interest Entity [Line Items]
Total assets	$ 7	$ 0