Financial Guarantee Insurance Contracts Financial Guarantee Insurance Contracts - Components of Loss and Loss Expense Reserves and Subrogation Recoverable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Policyholder Benefits and Claims Incurred, Ceded	$ 110	$ 41	$ (5)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	577	883	(578)	$ (430)
Subrogation recoverable	(137)	(271)
Claim liability reported on Balance Sheet, before reinsurance		444
Liability for Claims and Claims Adjustment Expense	893	805
Liabillity for Claim and Claim Adjustment Expense, with Impact of VIE Consolidation	756	534	(522)	$ (397)
Premiums Earned, Net	78	56	47
Legacy Financial Guarantee
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Liability for Claims and Claims Adjustment Expense	696	715	1,538
Premiums Earned, Net	26	42	$ 46
Property and Casualty, Commercial Insurance
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Liability for Claims and Claims Adjustment Expense	197	90
Liabillity for Claim and Claim Adjustment Expense, with Impact of VIE Consolidation	197	90
Unearned Premium Reserve [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	0	0
Claim liability reported on Balance Sheet, before reinsurance	(28)	(28)
Liability for Claims and Claims Adjustment Expense	(28)	(28)
Present Value of Expected Net Cash Flows- Claims and Loss Expenses [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	1	5
Claim liability reported on Balance Sheet, before reinsurance	780	791
Liability for Claims and Claims Adjustment Expense	779	787
Present Value of Expected Net Cash Flows-Recoveries [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	(139)	(276)
Claim liability reported on Balance Sheet, before reinsurance	(194)	(319)
Liability for Claims and Claims Adjustment Expense	$ (55)	$ (44)