Insurance Claim Reserves (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	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		$ 54,521
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	$ 92	141	$ 146	$ 92
Net reserves at end of year		48,688
Reinsurance recoverables on unpaid losses		8,219
Claims and claim adjustment expense reserves at end of year		56,907	54,521
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			53	$ 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		54,510	51,836	50,653
Reinsurance recoverables on unpaid losses		8,153	8,035	8,182
Net reserves at beginning of year		46,357	43,801	42,471
Estimated claims and claim adjustment expenses for claims arising in the current year		20,698	19,285	18,854
Estimated increase (decrease) in claims and claim adjustment expenses for claims arising in prior years		(484)	(267)	164
Total increases		20,214	19,018	19,018
Claims and claim adjustment expense payments for claims arising in current year		8,401	7,497	7,734
Claims and claim adjustment expense payments for claims arising in prior years		9,470	9,092	10,060
Total payments		17,871	16,589	17,794
Unrealized foreign exchange loss (gain)		(12)	74	106
Net reserves at end of year	43,801	48,688	46,357	43,801
Reinsurance recoverables on unpaid losses	8,035	8,209	8,153	8,035
Claims and claim adjustment expense reserves at end of year	51,836	56,897	54,510	51,836
Amount of increase in gross claims and claim adjustment expense reserves		2,390	2,670
Amount of increase in reinsurance recoverables on unpaid losses		56	118
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		2,740	2,690
Discount included in reserves for long-term disability and annuity claim payments primarily arising from workers' compensation insurance and workers' compensation excess insurance policies		1,150	1,140
Accretion expense		$ 48	49	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			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			$ 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		$ 11
Net reserves at end of year		0
Reinsurance recoverables on unpaid losses		10
Claims and claim adjustment expense reserves at end of year		$ 10	$ 11