Reserve for Property and Casualty Insurance Claims and Claims Expense - Rollforward of reserve for property and casualty insurance claims and claims expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Incurred claims and claims expense related to:
Prior years	$ 122	$ (436)	$ (130)
Total incurred	29,318	22,001	23,976
Property and casualty
Activity in the reserve for property-liability insurance claims and claims expense:
Balance as of January 1	27,610	27,712	27,423
Less recoverables	(7,033)	(6,912)	(7,155)
Net balance as of January 1	20,577	20,800	20,268
Incurred claims and claims expense related to:
Current year	29,196	22,437	24,106
Prior years	122	(436)	(130)
Total incurred	29,318
Claims and claims expense paid related to:
Current year	(18,438)	(14,245)	(15,160)
Prior years	(9,807)	(7,979)	(8,284)
Total paid	(28,245)	(22,224)	(23,444)
Net balance as of December 31	23,581	20,577	20,800
Plus recoverables	(9,479)	(7,033)	(6,912)
Balance as of December 31	33,060	27,610	27,712
Property and casualty | National General Holdings Corp.
Activity in the reserve for property-liability insurance claims and claims expense:
National General acquisition as of January 4, 2021	1,797	0	0
Property and casualty | SafeAuto
Activity in the reserve for property-liability insurance claims and claims expense:
National General acquisition as of January 4, 2021	$ 134	$ 0	$ 0