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		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Incurred claims and claims expense related to:
Prior years	$ 212	$ 459	$ 197	$ 604
Property and casualty
Property-liability insurance claims and claims expense
Balance as of January 1	40,531	34,276	40,531	34,276	$ 37,541	$ 33,060
Less recoverables	8,730	8,950	8,730	8,950	9,176	9,479
Activity in the reserve for property-liability insurance claims and claims expense:
Net balance as of January 1			28,365	23,581
Incurred claims and claims expense related to:
Current year			21,856	16,585
Prior years			197	604
Total incurred			22,053	17,189
Claims and claims expense paid related to:
Current year			(9,094)	(7,753)
Prior years			(9,523)	(7,691)
Total paid			(18,617)	(15,444)
Net balance as of June 30	31,801	25,326	31,801	25,326
Plus recoverables	8,730	8,950	8,730	8,950	9,176	9,479
Balance as of June 30	$ 40,531	$ 34,276	$ 40,531	$ 34,276	$ 37,541	$ 33,060