Allowance for Expected Credit Losses (Details) - Changes in the Allowance for Estimated Uncollectible Reinsurance - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Reinsurance recoverables, allowance for uncollectible reinsurance
Reinsurance recoverables (net of allowance for estimated uncollectible reinsurance), balance, beginning of period	$ 8,093	$ 8,235
Reinsurance recoverables (net of allowance for estimated uncollectible reinsurance), balance, end of period	8,317	8,317
Reinsurance recoverables, allowance for uncollectible reinsurance [Roll Forward]
Reinsurance recoverables, allowance for uncollectible reinsurance, beginning balance	156	92
Reinsurance recoverables, allowance for estimated uncollectible reinsurance	140	$ 140
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member
Current period change for estimated uncollectible reinsurance	(16)	$ (5)
Write-offs of uncollectible reinsurance recoverables	0	0
Reinsurance recoverables, allowance for uncollectible reinsurance, ending balance	$ 140	140
Cumulative Effect, Period of Adoption, Adjustment [Member]
Reinsurance recoverables, allowance for uncollectible reinsurance [Roll Forward]
Reinsurance recoverables, allowance for uncollectible reinsurance, beginning balance		53
Reinsurance recoverables, allowance for estimated uncollectible reinsurance		$ 53