Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($) Entity	Sep. 30, 2022 USD ($) entity Entity	Sep. 30, 2021 USD ($) Entity	Sep. 30, 2022 USD ($)	Sep. 30, 2022 Entity	Sep. 30, 2022 entity	Sep. 30, 2022 consolidatedInvestmentVehicle	Sep. 30, 2022 policy	Dec. 31, 2021 USD ($)	Dec. 31, 2021 Entity	Dec. 31, 2021 consolidatedInvestmentVehicle	Dec. 31, 2021 policy	Dec. 31, 2020 Entity
Variable Interest Entity [Line Items]
Liabilities					$ 11,486,000,000					$ 11,708,000,000
Estimated Fair Value					6,780,000,000					8,202,000,000
Amortized Cost					7,506,000,000					7,822,000,000
Fixed-maturity securities, trading					393,000,000					0
Net fair value gains and losses on FG VIEs are expected to reverse to zero at maturity of the VIE debt					1,000,000					1,000,000
Assets					16,660,000,000					18,208,000,000
Fair value gains (losses) on credit derivatives	$ (48,000,000)	$ 21,000,000	$ (42,000,000)	$ (31,000,000)
Other consolidated VIE assets					85,000,000					96,000,000
Other consolidated VIE liabilities					14,000,000					11,000,000
Number of policies monitored | policy									16,000
Number of policies monitored, not within the scope of ASC 810 | policy									14,000
Number of policies that contain provisions for consolidation | policy									63				69
Pretax income (loss)	(22,000,000)	5,000,000	49,000,000	145,000,000
Total consolidated	11,000,000	17,000,000	30,000,000	$ 126,000,000
Variable Interest Entity, Correction of Fair Value | Revision of Prior Period, Error Correction, Adjustment
Variable Interest Entity [Line Items]
Pretax income (loss)			6,600,000
Total consolidated			5,200,000
Incorrect Elimination of Foreign Exchange Remeasurement | Revision of Prior Period, Error Correction, Adjustment
Variable Interest Entity [Line Items]
Pretax income (loss)			2,100,000
Total consolidated			$ 1,700,000
Joint Healthcare Fund | Line of Credit
Variable Interest Entity [Line Items]
Maximum borrowing capacity					110,000,000
Long-term line of credit					62,000,000
Consolidated Healthcare Fund | Line of Credit
Variable Interest Entity [Line Items]
Maximum borrowing capacity					71,000,000
Prime Rate | Joint Healthcare Fund | Line of Credit
Variable Interest Entity [Line Items]
Base interest rate floor			3.00%
EURIBOR | Joint Healthcare Fund | Line of Credit
Variable Interest Entity [Line Items]
Base interest rate floor			0.00%
Financial Guaranty Variable Interest Entities
Variable Interest Entity [Line Items]
Maximum loss exposure					0
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total number of entities consolidated | Entity						24					25
Number of entities consolidated during period | Entity			1
Number of entities deconsolidated during period | Entity			(2)	1
Change in the instrument specific credit risk of the VIEs' assets	$ 15,000,000	$ 5,000,000	$ 11,000,000	$ 9,000,000
Assets					236,000,000					260,000,000
Financial Guaranty Variable Interest Entities | Puerto Rico | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets					26,000,000					0
Puerto Rico Trusts | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total number of entities consolidated | entity							6
Number of entities consolidated during period | entity			9
Number of entities deconsolidated during period | entity			3
Custody receipts, notice period	30 days		30 days
Estimated Fair Value					21,000,000
Amortized Cost					24,000,000
Fixed-maturity securities, trading					6,000,000
Trading security losses			$ 1,000,000
Initial consolidation, gain (loss)			(4,000,000)
Deconsolidation, gain (loss)			(1,000,000)
Consolidated Investment Vehicles
Variable Interest Entity [Line Items]
Collateral posting requirement					45,000,000					49,000,000
Fair value gains (losses) on credit derivatives			$ 7,000,000	$ 1,000,000
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total number of entities consolidated		16		16		22		22			20	20		11
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Maximum borrowing capacity					1,500,000,000
Remaining borrowing capacity					337,000,000
Long-term line of credit					206,000,000
Consolidated Investment Vehicles | EURIBOR | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Basis spread on variable rate			1.50%
Consolidated Investment Vehicles | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Basis spread on variable rate			1.50%
Consolidated Investment Vehicles | Maximum | Future Equity Investments
Variable Interest Entity [Line Items]
Committed capital			$ 442,000,000
Consolidated Investment Vehicles | Average
Variable Interest Entity [Line Items]
Collateral posting requirement					47,000,000					34,000,000
Consolidated Investment Vehicles, Meeting Voting Interest Entity Criteria | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total number of entities consolidated | consolidatedInvestmentVehicle								2				1
Liabilities					2,000,000
Assets					69,000,000					$ 12,000,000
Fund investments: | Variable Interest Entity, Primary Beneficiary | Investments
Variable Interest Entity [Line Items]
Liabilities					26,000,000
Net assets					125,000,000
Assets					$ 150,000,000