Reserve for Property and Casualty Insurance Claims and Claims Expense - Rollforward of the reserve for property and casualty insurance claims and claims expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Incurred claims and claims expense related to:
Prior years	$ (15)	$ 145
Property and casualty
Activity in the reserve for property-liability insurance claims and claims expense:
Beginning balance	37,541	33,060
Less recoverables	(9,176)	(9,479)
Net balance as of January 1	28,365	23,581
Incurred claims and claims expense related to:
Current year	10,341	7,677
Prior years	(15)	145
Total incurred	10,326	7,822
Claims and claims expense paid related to:
Current year	(3,122)	(2,751)
Prior years	(6,036)	(4,735)
Total paid	(9,158)	(7,486)
Net balance as of March 31	29,533	23,917
Plus recoverables	(9,111)	(9,074)
Ending balance	$ 38,644	$ 32,991