Insurance Claim Reserves (Details) - Reserve Detail for Claims and Claim Adjustment Expenses - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
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	$ 56,907
Claims and claim adjustment expense reserves at end of period	57,572
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	56,897	$ 54,510
Reinsurance recoverables on unpaid losses	8,209	8,153
Net reserves at beginning of year	48,688	46,357
Estimated claims and claim adjustment expenses for claims arising in the current year	5,133	5,242
Estimated decrease in claims and claim adjustment expenses for claims arising in prior years	(114)	(294)
Total increases	5,019	4,948
Claims and claim adjustment expense payments for claims arising in current year	1,074	1,059
Claims and claim adjustment expense payments for claims arising in prior years	3,498	3,012
Total payments	4,572	4,071
Unrealized foreign exchange (gain) loss	(13)	28
Net reserves at end of period	49,122	47,262
Reinsurance recoverables on unpaid losses	8,441	8,068
Claims and claim adjustment expense reserves at end of period	57,563	$ 55,330
Amount of increase in gross claims and claim adjustment expense reserves	666
Amount of increase in reinsurance recoverables on unpaid losses	232
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	10
Claims and claim adjustment expense reserves at end of period	$ 9