Claim and Claim Adjustment Expense Reserves (International - Net prior year claim and allocated claim adjustment expense reserve development) (Details) - International - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Liability for Claims and Claims Adjustment Expense [Line Items]
Commercial Auto	$ (15)	$ (3)	$ (15)	$ (3)
Specialty	15	4	15	4
Other	0	(1)	0	(1)
Total pretax (favorable) unfavorable development	$ 0	$ 0	$ 0	$ 0