Financial Guaranty Variable Interest Entities and Consolidated Investment Vehicles - Narrative (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) fund entity	Dec. 31, 2021 USD ($) fund	Dec. 31, 2020 USD ($) Entity fund	Dec. 31, 2022 USD ($)	Dec. 31, 2022 Security	Dec. 31, 2022 Entity	Dec. 31, 2022 entity	Dec. 31, 2022 consolidatedInvestmentVehicle	Dec. 31, 2022 policy	Dec. 31, 2021 Security	Dec. 31, 2021 Entity	Dec. 31, 2021 consolidatedInvestmentVehicle	Dec. 31, 2021 policy	Dec. 31, 2019 Entity
Variable Interest Entity [Line Items]
Fixed-maturity securities, available-for-sale:		$ 8,202,000,000		$ 7,119,000,000
Amortized Cost		7,822,000,000		7,707,000,000
Fixed-maturity securities, trading, at fair value		0		303,000,000
Less than 12 months (in securities) | Security					1,340					355
Fair Value		804,000,000		3,751,000,000
Total assets		18,208,000,000		16,843,000,000
Total liabilities		11,708,000,000		11,551,000,000
Consolidation		89,000,000
Fair value gains (losses) on credit derivatives	$ (11,000,000)	(58,000,000)	$ 81,000,000
VIE, Other consolidated, carrying amount, assets		96,000,000		86,000,000
VIE, Other consolidated, carrying amount, liabilities		11,000,000		12,000,000
VIE, Number of policies monitored | policy									15,000
VIE, Number of policies monitored, not within the scope of ASC 810 | policy									14,000
VIE, Number of policies that contain provisions for consolidation | policy									85				69
Maximum loss exposure		1,000,000		1,000,000
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Net loss on consolidation	0	0
Net gain on deconsolidation	$ 0
Joint Healthcare Fund | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Maximum borrowing capacity				110,000,000
Outstanding amount				58,000,000
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%
Other | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Net gain on deconsolidation		0
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Change in the instrument specific credit risk of the VIEs' assets	$ 10,000,000	14,000,000	$ 6,000,000
Total assets		260,000,000		416,000,000
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
Number of entities consolidated during period | entity	48
Number of entities deconsolidated during period | entity	3
Fixed-maturity securities, available-for-sale:				204,000,000
Amortized Cost				204,000,000
Fixed-maturity securities, trading, at fair value				5,000,000
Trading security losses	$ 1,000,000
Gross Unrealized Gains				4,000,000
Gross unrealized losses				4,000,000
Less than 12 months (in securities) | Security					14
Fair Value				110,000,000
Securities in excess of carrying value | Security					8
Value securities in excess of carrying value				3,000,000
Total assets		0		212,000,000
Variable Interest Entity, Number of Entities Per Legacy Insured Bond | entity	1
Financial Guaranty Variable Interest Entities | Variable Interest Entity, Primary Beneficiary | Structured Finance and Other
Variable Interest Entity [Line Items]
Number of entities | Entity			25			25					25			27
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			11			22		22			20	20
Total assets		5,271,000,000		5,493,000,000
Fair value gains (losses) on credit derivatives	$ 3,000,000
Number of entities | Entity			11								20			4
Consolidated Investment Vehicles | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Maximum borrowing capacity				1,600,000,000
Proceeds from issuance of warehouse financing debt	$ 284,000,000
Remaining borrowing capacity				377,000,000
Consolidated Investment Vehicles | Assured IM | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets		273,000,000
Total liabilities		$ 33,000,000
Consolidated Investment Vehicles | CLO Warehouse | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Number of financial assets securitized | fund	2	5	2
Consolidated Investment Vehicles | Investments | Fund Investments | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Net assets				127,000,000
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]
Interest rate, added to base rate (as a percent)	1.50%
Consolidated Investment Vehicles | EURIBOR | Variable Interest Entity, Primary Beneficiary | Line of Credit
Variable Interest Entity [Line Items]
Interest rate, added to base rate (as a percent)	2.00%
Consolidated Investment Vehicles | Foreign Exchange Forward | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Derivative, notional amount				46,000,000
Consolidated Investment Vehicles | Interest Rate Swap | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Derivative, notional amount				49,000,000
Consolidated Investment Vehicles | Maximum | Future Equity Investments | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Investment commitment	$ 424,000,000
Consolidated Investment Vehicles | Arithmetic Average | Foreign Exchange Forward | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Derivative, notional amount				47,000,000
Consolidated Investment Vehicles | Arithmetic Average | Interest Rate Swap | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Derivative, notional amount				$ 34,000,000
Consolidated Investment Vehicles | Assured IM | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Gain consolidation		$ 31,000,000
Consolidation		$ 89,000,000