Insurance Claim Reserves (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2020
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
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Reinsurance recoverables, allowance for estimated uncollectible reinsurance		132	$ 141	$ 146
Net reserves at end of year		50,853
Reinsurance recoverables on unpaid losses		7,796
Claims and claim adjustment expense reserves at end of year		58,649	56,907
Cumulative Effect, Period of Adoption, Adjustment [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Reinsurance recoverables, allowance for estimated uncollectible reinsurance					$ 53
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	51,836
Reinsurance recoverables on unpaid losses		8,209	8,153	8,035
Net reserves at beginning of year		48,688	46,357
Estimated claims and claim adjustment expenses for claims arising in the current year		23,308	20,698	19,285
Estimated decrease in claims and claim adjustment expenses for claims arising in prior years		(537)	(484)	(267)
Total increases		22,771	20,214	19,018
Claims and claim adjustment expense payments for claims arising in current year		9,406	8,401	7,497
Claims and claim adjustment expense payments for claims arising in prior years		10,945	9,470	9,092
Total payments		20,351	17,871	16,589
Unrealized foreign exchange loss (gain)		(255)	(12)	74
Net reserves at end of year		50,853	48,688	46,357
Reinsurance recoverables on unpaid losses	$ 8,035	7,790	8,209	8,153
Claims and claim adjustment expense reserves at end of year	51,836	58,643	56,897	54,510
Amount of increase in gross claims and claim adjustment expense reserves		1,750	2,390
Amount of increase (decrease) in reinsurance recoverables on unpaid losses		(419)	56
Subrogation benefit recognized in earnings				403
Reserves for long-term disability and annuity claim payments primarily arising from workers' compensation insurance and workers' compensation excess insurance policies, net of discount		2,720	2,740
Discount included in reserves for long-term disability and annuity claim payments primarily arising from workers' compensation insurance and workers' compensation excess insurance policies		1,120	1,150
Accretion expense		$ 46	$ 48	49
Property-casualty [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	53
Property-casualty [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Net reserves at beginning of year				$ 43,854
Net reserves at end of year	$ 43,854
Property-casualty [Member] | Minimum [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Reserves for long-term disability and annuity claim payments primarily arising from workers' compensation insurance and workers' compensation excess insurance policies, discount rate (percent)		3.50%	3.50%
Property-casualty [Member] | Maximum [Member]
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]
Reserves for long-term disability and annuity claim payments primarily arising from workers' compensation insurance and workers' compensation excess insurance policies, discount rate (percent)		5.00%	5.00%
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
Net reserves at end of year		0
Reinsurance recoverables on unpaid losses		6
Claims and claim adjustment expense reserves at end of year		$ 6	$ 10