Segment Information (Reconciliation of Net Investment Income From Segments to Consolidated) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Investment Income [Abstract]
Total net investment income	$ 5,085	$ 4,990	$ 4,874
Annuities Segment [Member]
Net Investment Income [Abstract]
Total net investment income	1,005	1,038	1,033
Retirement Plan Services Segment [Member]
Net Investment Income [Abstract]
Total net investment income	899	899	859
Life Insurance Segment [Member]
Net Investment Income [Abstract]
Total net investment income	2,697	2,643	2,562
Group Protection Segment [Member]
Net Investment Income [Abstract]
Total net investment income	260	168	176
Other Operations [Member]
Net Investment Income [Abstract]
Total net investment income	$ 224	$ 242	$ 244