Reinsurance - Effects of Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Premiums Earned, Net [Abstract]
Direct	$ 29,812	$ 27,215	$ 25,541
Assumed	400	602	577
Ceded	(570)	(603)	(543)
Premiums Earned Net	29,642	27,214	25,575
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	737	658	317
Individual Life Insurance And Annuity Business Sold [Member]
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	301	366	335
Other Subsegments [Member]
Reinsurance Recoveries [Abstract]
Reinsurance recoveries	436	292	(18)
Short Duration Contracts [Member]
Premiums Earned, Net [Abstract]
Direct	26,751	24,294	23,056
Assumed	289	429	394
Ceded	(254)	(226)	(252)
Premiums Earned Net	$ 26,786	$ 24,497	$ 23,198
Premiums Written, Net [Abstract]
Direct premiums, written versus earned
Assumed premiums, written versus earned
Ceded premiums, written versus earned
Net premiums, written versus earned
Long Duration Contracts [Member]
Premiums Earned, Net [Abstract]
Direct	$ 3,061	$ 2,921	$ 2,485
Assumed	111	173	183
Premiums Earned Net	2,856	2,717	2,377
Long Duration Contracts [Member] | Individual Life Insurance And Annuity Business Sold [Member]
Premiums Earned, Net [Abstract]
Ceded	(158)	(254)	(176)
Long Duration Contracts [Member] | Other Subsegments [Member]
Premiums Earned, Net [Abstract]
Ceded	$ (158)	$ (123)	$ (115)