Claim and Claim Adjustment Expense Reserves (Impact of Loss Portfolio Transfer on the Consolidated Statement of Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Net A&EP adverse development before consideration of LPT	$ 185	$ 103	$ 86
Asbestos and Environmental Reserves
Liability for Claims and Claims Adjustment Expense [Line Items]
Additional amounts ceded under LPT	185	103	86
Retroactive reinsurance benefit recognized	(140)	(95)	(94)
Pretax impact of deferred retroactive reinsurance	$ 45	$ 8	$ (8)