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, 2022	Dec. 31, 2021	Dec. 31, 2020
Incurred claims and claims expense related to:
Prior years	$ 1,741	$ 122	$ (436)
Total incurred	37,264	29,318	22,001
Property and casualty
Activity in the reserve for property-liability insurance claims and claims expense:
Balance as of January 1	33,060	27,610	27,712
Less recoverables	(9,479)	(7,033)	(6,912)
Net balance as of January 1	23,581	20,577	20,800
Incurred claims and claims expense related to:
Current year	35,523	29,196	22,437
Prior years	1,741	122	(436)
Total incurred	37,264
Claims and claims expense paid related to:
Current year	(20,739)	(18,438)	(14,245)
Prior years	(11,741)	(9,807)	(7,979)
Total paid	(32,480)	(28,245)	(22,224)
Net balance as of December 31	28,365	23,581	20,577
Plus recoverables	(9,176)	(9,479)	(7,033)
Balance as of December 31	37,541	33,060	27,610
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	0	1,797	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	$ 0	$ 134	$ 0