Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022
Variable Interest Entity [Line Items]
Assets	$ 16,852	$ 16,843
Liabilities	11,397	11,551
Cash	114	107	$ 138
Variable Interest Entity, Primary Beneficiary | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	687	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 | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	493	495
Variable Interest Entity, Primary Beneficiary | Underlying, Other | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	7	7
Variable Interest Entity, Primary Beneficiary | United States | RMBS | First Lien | Recourse | Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Liabilities	165	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	22	24
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	414	416
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts
Variable Interest Entity [Line Items]
Assets	226	212
Total assets carried at fair value	223	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	154	167
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | United States | RMBS | Second Lien
Variable Interest Entity [Line Items]
Assets	$ 27	$ 30