Reinsurance - Effects of Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Premiums Earned, Net [Abstract]
Ceded	$ 120	$ 136
Premiums Earned Net	8,103	7,746
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	99	164
Individual Life Insurance And Annuity Business Sold [Member]
Premiums Earned, Net [Abstract]
Ceded	39	41
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	70	68
Other Subsegments [Member]
Premiums Earned, Net [Abstract]
Ceded	81	95
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	$ 29	$ 96