Segment Information (Reconciliation Of Income (Loss) From Operations By Segment To Consolidated Net Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Acquisition and integration costs related to mergers and acquisitions, after tax	$ (10)		$ (60)
Net income (loss)	490	$ 418	1,242	$ 1,264
Segment Reconciling Items [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Excluded realized gain (loss), after-tax	(77)	(63)	(149)	(149)
Gain (loss) on early extinguishment of debt, after-tax		(3)	(18)	(3)
Income (loss) from reserve changes (net of related amortization) on business sold through reinsurance, after tax				1
Benefit ratio unlocking, after-tax	33	30	32	101
Net impact from the Tax Cuts and Jobs Act	32		19
Acquisition and integration costs related to mergers and acquisitions, after tax	(8)		(47)
Annuities Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	302	277	844	809
Retirement Plan Services Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	40	35	125	109
Life Insurance Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	176	121	470	384
Group Protection Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	63	41	137	83
Other Operations [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	$ (71)	$ (20)	$ (171)	$ (71)