Segment Information (Reconciliation Of Income (Loss) From Operations By Segment To Consolidated Net Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Acquisition and integration costs related to mergers and acquisitions, after tax	$ (44)		$ (50)
Net income (loss)	385	$ 411	752	$ 846
Segment Reconciling Items [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Excluded realized gain (loss), after-tax	(41)	(34)	(69)	(85)
Gain (loss) on early extinguishment of debt, after-tax			(19)
Benefit ratio unlocking, after-tax	7	26	(3)	71
Net impact from the Tax Cuts and Jobs Act			(13)
Acquisition and integration costs related to mergers and acquisitions, after tax	(35)		(39)
Annuities Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	275	251	542	532
Retirement Plan Services Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	43	37	86	74
Life Insurance Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	150	133	294	263
Group Protection Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	45	35	74	42
Other Operations [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	$ (59)	$ (37)	$ (101)	$ (51)