Contracts Accounted for as Insurance - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Guarantor Obligations [Line Items]
Weighted average risk-free rates for U.S. dollar denominated financial guaranty insurance obligations	4.15%	1.02%
Net Par Outstanding	$ 233,258	$ 236,392
Gross	370,172	367,770
Increase (decrease) in net par due to commutations			$ 336
Commutation gains (losses)	2	0	38
Gross Exposure	1,700
Puerto Rico
Guarantor Obligations [Line Items]
Net Par Outstanding	1,361	3,572
Gross	1,899	5,322
Net par exposures reassumed			$ 118
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement
Guarantor Obligations [Line Items]
Net Par Outstanding	509	$ 2,643
Puerto Rico | Puerto Rico Exposures Subject to a Plan Support Agreement | HTA/CCDA PSA
Guarantor Obligations [Line Items]
Outstanding principal amount of amended plan election, net	451
Assumed Business
Guarantor Obligations [Line Items]
Insured financial obligations insured contractual payments outstanding, amount represented	$ 14,000
Insured financial obligations insured contractual payments outstanding, percentage represented	3.80%
AGC
Guarantor Obligations [Line Items]
Amounts could be required to pay if third party exercised right to recapture business	$ 234
AG Re
Guarantor Obligations [Line Items]
Amounts could be required to pay if third party exercised right to recapture business	34
Ceded Business
Guarantor Obligations [Line Items]
Insured financial obligations insured contractual payments outstanding, amount represented	$ 221
Insured financial obligations insured contractual payments outstanding, percentage represented	0.10%
Gross Insured Specialty and Reinsurance Business
Guarantor Obligations [Line Items]
Insured financial obligations insured contractual payments outstanding, amount represented	$ 483
ARGO | Uncollateralized
Guarantor Obligations [Line Items]
Guaranty liabilities	$ 12
Minimum
Guarantor Obligations [Line Items]
Risk free discount rate	3.82%	0.00%
Maximum
Guarantor Obligations [Line Items]
Risk free discount rate	4.69%	1.98%
Premiums Receivable | Foreign Currency Concentration Risk | Premiums Receivable
Guarantor Obligations [Line Items]
Percentage of installment premiums denominated in currencies other than the U.S. dollar	74.00%	78.00%