Insurance Claim Reserves (Details) - Reserve Detail for Claims and Claim Adjustment Expenses - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year	$ 58,649
Claims and claim adjustment expense reserves at end of period	61,709
Property-casualty [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year	58,643	$ 56,897
Reinsurance recoverables on unpaid losses	7,790	8,209
Net reserves at beginning of year	50,853	48,688
Estimated claims and claim adjustment expenses for claims arising in the current year	20,205	17,257
Estimated increase (decrease) in claims and claim adjustment expenses for claims arising in prior years	62	(383)
Total increases	20,267	16,874
Claims and claim adjustment expense payments for claims arising in current year	7,305	6,302
Claims and claim adjustment expense payments for claims arising in prior years	10,031	8,638
Total payments	17,336	14,940
Unrealized foreign exchange gain	(1)	(391)
Net reserves at end of period	53,783	50,231
Reinsurance recoverables on unpaid losses	7,920	7,900
Claims and claim adjustment expense reserves at end of period	61,703	$ 58,131
Amount of increase in gross claims and claim adjustment expense reserves	3,060
Amount of increase in reinsurance recoverables on unpaid losses	130
Accident and health [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Claims and claim adjustment expense reserves at beginning of year	6
Claims and claim adjustment expense reserves at end of period	$ 6