Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Additional Information (Details)	3 Months Ended
	Mar. 31, 2023 USD ($) entity policy consolidatedInvestmentVehicle Security Entity	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($) consolidatedInvestmentVehicle Security entity Entity policy
Variable Interest Entity [Line Items]
Estimated Fair Value	$ 6,869,000,000		$ 7,119,000,000
Amortized Cost	7,359,000,000		7,707,000,000
Fixed-maturity securities, trading	300,000,000		303,000,000
Gross Unrealized Gains	75,000,000		65,000,000
Gross Unrealized Losses	$ 496,000,000		$ 588,000,000
Number of securities | Security	1,006		466
Number of securities | Security	602		1,340
Fair Value	$ 2,499,000,000		$ 1,017,000,000
Fair Value	1,584,000,000		3,751,000,000
Fair value gains (losses) on credit derivatives	15,000,000	$ (3,000,000)
Other consolidated VIE assets	89,000,000		86,000,000
Other consolidated VIE liabilities	$ 10,000,000		$ 12,000,000
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	86		85
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
Joint Healthcare Fund | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Maximum borrowing capacity	110,000,000
Long-term line of credit	28,000,000
Consolidated Healthcare Fund | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Maximum borrowing capacity	$ 71,000,000
Prime Rate | Joint Healthcare Fund | Variable Interest Entity, Primary Beneficiary | 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%
CLOs and CLO warehouse assets:
Variable Interest Entity [Line Items]
Fair Value	$ 377,000,000		250,000,000
Fair Value	42,000,000		$ 171,000,000
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Maximum loss exposure	0
Change in the instrument specific credit risk of the VIEs' assets	$ 1,000,000	5,000,000
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Puerto Rico Trusts
Variable Interest Entity [Line Items]
Total number of entities consolidated | entity	45		45
Estimated Fair Value	$ 211,000,000		$ 204,000,000
Amortized Cost	204,000,000		204,000,000
Fixed-maturity securities, trading	5,000,000		5,000,000
Gross Unrealized Gains	10,000,000		4,000,000
Gross Unrealized Losses	$ 3,000,000		$ 4,000,000
Number of securities | Security	12
Number of securities | Security			14
Fair Value	$ 21,000,000
Fair Value			$ 110,000,000
Securities in excess of carrying value | Security	6		8
Unrealized losses for securities	$ 2,000,000		$ 3,000,000
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	25		25
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	21		22
Collateral posting requirement	$ 39,000,000		$ 46,000,000
Fair value gains (losses) on credit derivatives		$ 4,000,000
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Maximum borrowing capacity	1,600,000,000
Remaining borrowing capacity	252,000,000
Borrowing (payment) under credit facilities	$ 138,000,000
Consolidated Investment Vehicles | Voting Interest Entity
Variable Interest Entity [Line Items]
Total number of entities consolidated | consolidatedInvestmentVehicle	1		2
Consolidated Investment Vehicles | EURIBOR | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Basis spread on variable rate	2.50%
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	$ 453,000,000
Consolidated Investment Vehicles | Average | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Collateral posting requirement	$ 43,000,000		$ 47,000,000
Consolidated Investment Vehicles | Fund investments: | Variable Interest Entity, Primary Beneficiary | Investments
Variable Interest Entity [Line Items]
Net assets			$ 127,000,000