Segment Information (Reconciliation of Net Investment Income from Segments to Consolidated Net Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Investment Income [Abstract]
Total net investment income	$ 4,827	$ 4,859	$ 4,754
Parent Company [Member]
Net Investment Income [Abstract]
Total net investment income		1
Annuities Segment [Member]
Net Investment Income [Abstract]
Total net investment income	1,004	1,033	1,044
Retirement Plan Services Segment [Member]
Net Investment Income [Abstract]
Total net investment income	846	831	827
Life Segment [Member]
Net Investment Income [Abstract]
Total net investment income	2,541	2,529	2,452
Group Protection Segment [Member]
Net Investment Income [Abstract]
Total net investment income	184	180	165
Other Operations [Member]
Net Investment Income [Abstract]
Total net investment income	$ 252	$ 286	$ 266