Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Variable Interest Entity [Line Items]
Assets	$ 16,778	$ 16,843
Liabilities	11,363	11,551
Cash	118	107	$ 119
Variable Interest Entity, Primary Beneficiary | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	692	702
Variable Interest Entity, Primary Beneficiary | Nonrecourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	12	13
Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	487	495
Variable Interest Entity, Primary Beneficiary | Underlying, Other | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	8	7
Variable Interest Entity, Primary Beneficiary | United States | RMBS | First Lien | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	173	176
Variable Interest Entity, Primary Beneficiary | United States | RMBS | First Lien | Nonrecourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	12	13
Variable Interest Entity, Primary Beneficiary | United States | RMBS | Second Lien | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	24	24
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	415	416
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts
Variable Interest Entity [Line Items]
Assets	217	212
Total assets carried at fair value	215	209
Cash		2
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Underlying, Other
Variable Interest Entity [Line Items]
Assets	7	7
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | United States | RMBS | First Lien
Variable Interest Entity [Line Items]
Assets	161	167
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | United States | RMBS | Second Lien
Variable Interest Entity [Line Items]
Assets	$ 30	$ 30