Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Impact of Loss Portfolio Transfer on the Consolidated Statement of Operations) (Details) - Asbestos and Environmental Reserves - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Net A&EP adverse development before consideration of LPT	$ 92	$ 143	$ 125
Provision for uncollectible third-party reinsurance on A&EP	(5)	(5)	(25)
Total additional amounts ceded under LPT	87	138	100
Retroactive reinsurance benefit recognized	(91)	(107)	(94)
Pretax impact of deferred retroactive reinsurance	$ (4)	$ 31	$ 6