Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Additional Information (Details)	3 Months Ended
	Mar. 31, 2024 USD ($) Entity policy consolidatedInvestmentVehicle entity	Dec. 31, 2023 USD ($) Entity entity policy consolidatedInvestmentVehicle
Variable Interest Entity [Line Items]
Number of policies monitored | policy	15,000
Number of policies monitored, not within the scope of ASC 810 | policy	14,000
Number of policies that contain provisions for consolidation | policy	60	68
Net fair value gains and losses on FG VIEs are expected to reverse to zero at maturity of the VIE debt	$ 395,000,000
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Other consolidated VIE assets		$ 92,000,000
Other consolidated VIE liabilities		$ 7,000,000
Deconsolidation, gain (loss)	5,000,000
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Maximum loss exposure	$ 0
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts
Variable Interest Entity [Line Items]
Total number of entities consolidated | entity	24	24
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Structured Finance and Other
Variable Interest Entity [Line Items]
Total number of entities consolidated | Entity	23	24
Puerto Rico Trusts | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Custody receipts, notice period	30 days
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total number of entities consolidated | consolidatedInvestmentVehicle	3	3
Consolidated Investment Vehicles | Average | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Collateral posting requirement	$ 38,000,000	$ 41,000,000