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	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Commercial Auto	$ 0	$ 0	$ 21	$ 30
General Liability	0	0	41	0
Workers' Compensation	(2)	2	(86)	(40)
Property and Other	0	0	(2)	12
Total pretax (favorable) unfavorable development	$ (2)	$ 2	$ (26)	$ 2