Claim and Claim Adjustment Expense Reserves, Reconciliation of Claim and Claim Adjustment Expense Reserves (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Adjustment Expense [Abstract]
Catastrophe losses, net of reinsurance		$ 75	$ 58
Catastrophe losses, net of reinsurance related to COVID-19 pandemic		13
Catastrophe losses, net of reinsurance related primarily to U.S. weather related events		62
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning of year		21,720	21,984
Ceded reserves, beginning of year		3,835	4,019
Net reserves, beginning of year		17,885	17,965
Net incurred claim and claim adjustment expenses [Abstract]
Provision for insured events of current year		1,355	1,309
Increase (decrease) in provision for insured events of prior years		(8)	8
Amortization of discount		51	50
Total net incurred	[1]	1,398	1,367
Net payments attributable to [Abstract]
Current year events		(72)	(100)
Prior year events		(1,218)	(1,309)
Total net payments		(1,290)	(1,409)
Foreign currency translation adjustment and other		(88)	13
Net reserves, end of period		17,905	17,936
Ceded reserves, end of period		3,967	3,900
Gross reserves, end of period		$ 21,872	$ 21,836

[1] Total net incurred above does not agree to Insurance claims and policyholders’ benefits as reflected on the Consolidated Condensed Statements of Operations due to amounts related to retroactive reinsurance deferred gain accounting, uncollectible reinsurance and benefit expenses related to future policy benefits, which are not reflected in the table above.