Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Variable Interest Entity [Line Items]
Total assets	$ 12,539	$ 16,843
Total liabilities	6,774	11,551
Cash	97	107	$ 120
Variable Interest Entity, Primary Beneficiary | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	543	702
Variable Interest Entity, Primary Beneficiary | Nonrecourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	11	13
Variable Interest Entity, Primary Beneficiary | RMBS | U.S. | First Lien | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	156	176
Variable Interest Entity, Primary Beneficiary | RMBS | U.S. | First Lien | Nonrecourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	11	13
Variable Interest Entity, Primary Beneficiary | RMBS | U.S. | Second Lien | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	21	24
Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	366	495
Variable Interest Entity, Primary Beneficiary | Other | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total liabilities	0	7
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Total assets	328	416
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | RMBS | U.S. | First Lien
Variable Interest Entity [Line Items]
Total assets	145	167
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | RMBS | U.S. | Second Lien
Variable Interest Entity [Line Items]
Total assets	28	30
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | Puerto Rico Trusts
Variable Interest Entity [Line Items]
Total assets	155	212
Asset, fair value	1	209
Cash	154	2
Variable Interest Entity, Primary Beneficiary | Financial Guaranty Variable Interest Entities | Other
Variable Interest Entity [Line Items]
Total assets	$ 0	$ 7