Claim, Claim Adjustment Expense 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, 2021	Dec. 31, 2020	Dec. 31, 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Commercial	$ 53	$ 33	$ (25)
General Liability	15	15	16
Workers' Compensation	(82)	(96)	(13)
Property and Other	8	41	(18)
Total pretax (favorable) unfavorable development	$ (6)	$ (7)	$ (40)