Insurance Claim Reserves (Details) - Reserve Detail for Claims and Claim Adjustment Expenses - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 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	59,064
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	6,025	5,133
Estimated decrease in claims and claim adjustment expenses for claims arising in prior years	(90)	(114)
Total increases	5,935	5,019
Claims and claim adjustment expense payments for claims arising in current year	1,177	1,074
Claims and claim adjustment expense payments for claims arising in prior years	4,382	3,498
Total payments	5,559	4,572
Unrealized foreign exchange (gain) loss	28	(13)
Net reserves at end of period	51,257	49,122
Reinsurance recoverables on unpaid losses	7,801	8,441
Claims and claim adjustment expense reserves at end of period	59,058	$ 57,563
Amount of increase in gross claims and claim adjustment expense reserves	415
Amount of increase in reinsurance recoverables on unpaid losses	11
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