Reinsurance - Effects of Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Premiums Earned, Net [Abstract]
Premiums Earned Net	$ 39,714	$ 36,113	$ 32,491
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	395	452	325
Premiums Written, Net [Abstract]
Direct premiums, written versus earned
Assumed premiums, written versus earned
Ceded Premiums Written Versus Earned
Net premiums, written versus earned
Individual Life Insurance And Annuity Business Sold [Member]
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	238	249	259
Other Subsegments [Member]
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	157	203	66
Short Duration Contracts [Member]
Premiums Earned, Net [Abstract]
Direct	35,690	32,148	28,838
Assumed	64	77	199
Ceded	(203)	(182)	(150)
Premiums Earned Net	35,551	32,043	28,887
Long Duration Contracts [Member]
Premiums Earned, Net [Abstract]
Direct	4,352	4,268	3,748
Assumed	105	116	130
Premiums Earned Net	4,163	4,070	3,604
Long Duration Contracts [Member] | Individual Life Insurance And Annuity Business Sold [Member]
Premiums Earned, Net [Abstract]
Ceded	(126)	(133)	(143)
Long Duration Contracts [Member] | Other Subsegments [Member]
Premiums Earned, Net [Abstract]
Ceded	$ (168)	$ (181)	$ (131)