Insurance Contracts Financial Guarantee Insurance Contracts - Components of Loss and Loss Expense Reserves and Subrogation Recoverable (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered		$ 0
Policyholder Benefits and Claims Incurred, Ceded	$ 45	14
Subrogation recoverable	(139)		$ (271)
Claim liability reported on Balance Sheet, before reinsurance	594		444
Liability for Claims and Claims Adjustment Expense	863		805
Liability for Claim and Claim Adjustment Expenses Net of Subrogation recoverables	724	$ (647)	534	$ (522)
Property and Casualty, Commercial Insurance
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Liability for Claims and Claims Adjustment Expense	130		90
Liability for Claim and Claim Adjustment Expenses Net of Subrogation recoverables	130		90
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	2		5
Claim liability reported on Balance Sheet, before reinsurance	815		791
Liability for Claims and Claims Adjustment Expense	813		787
Present Value of Expected Net Cash Flows-Recoveries [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	(140)		(276)
Claim liability reported on Balance Sheet, before reinsurance	(190)		(319)
Liability for Claims and Claims Adjustment Expense	(50)		(44)
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	(31)		(28)
Liability for Claims and Claims Adjustment Expense	$ (31)		$ (28)