Contracts Accounted for as Insurance - Reconciliation of Net Expected Loss to be Paid and Expensed (Details) - USD ($) $ in Millions	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Guarantor Obligations [Line Items]
Net expected loss to be paid (recovered) - financial guaranty insurance	$ (560)	$ (517)	$ (522)	$ (442)	$ (432)	$ (411)
Net expected loss to be expensed	204
Financial Guarantee Insurance And Other Product Line
Guarantor Obligations [Line Items]
Net expected loss to be paid (recovered) - financial guaranty insurance	259
Contra-paid, net	22
Salvage and subrogation recoverable, net	266
Loss and LAE reserve - financial guaranty insurance contracts, net of reinsurance	(343)
Net expected loss to be expensed	$ 204