Segment Information (Reconciliation of Net Investment Income from Segments to Consolidated Net Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Investment Income [Abstract]
Total net investment income	$ 4,859	$ 4,754	$ 4,698
Parent Company [Member]
Net Investment Income [Abstract]
Total net investment income	1		1
Annuities [Member]
Net Investment Income [Abstract]
Total net investment income	1,033	1,044	1,082
Retirement Plan Services [Member]
Net Investment Income [Abstract]
Total net investment income	831	827	799
Life Insurance [Member]
Net Investment Income [Abstract]
Total net investment income	2,529	2,452	2,396
Group Protection [Member]
Net Investment Income [Abstract]
Total net investment income	180	165	162
Other Operations [Member]
Net Investment Income [Abstract]
Total net investment income	$ 286	$ 266	$ 259