Contracts Accounted for as Insurance - Reconciliation of Net Expected Loss to be Paid and Expensed (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Guarantor Obligations [Line Items]
Net Expected Loss to be Paid (Recovered)	$ 411	$ 529	$ 737	$ 1,183
Loss and LAE reserve - financial guaranty insurance contracts, net of reinsurance	(864)	$ (1,080)
Net expected loss to be expensed (present value)	325
Financial Guarantee Insurance And Other Product Line
Guarantor Obligations [Line Items]
Net Expected Loss to be Paid (Recovered)	359
Contra-paid, net	40
Salvage and subrogation recoverable, net	785
Loss and LAE reserve - financial guaranty insurance contracts, net of reinsurance	(859)
Net expected loss to be expensed (present value)	$ 325