Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Commercial - Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development) (Details) - Commercial - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Commercial	$ 49	$ 53	$ 33
General Liability	67	15	15
Workers' Compensation	(152)	(82)	(96)
Property and Other	(7)	8	41
Total pretax (favorable) unfavorable development	$ (43)	$ (6)	$ (7)