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		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Commercial	$ 0	$ 0	$ (5)	$ (4)
Specialty	0	0	22	(1)
Other	0	0	(2)	0
Total pretax (favorable) unfavorable development	$ 0	$ 0	$ 15	$ (5)