Segment Information (Reconciliation Of Income (Loss) From Operations By Segment To Consolidated Net Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended										12 Months Ended
	Dec. 31, 2017	[1]	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	[1]	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)	$ 816		$ 418	$ 411	$ 435	$ 189		$ 467	$ 325	$ 211	$ 2,079	$ 1,192	$ 1,154
Annuities Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											1,074	935	996
Retirement Plan Services Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											149	127	140
Life Insurance Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											536	515	370
Group Protection Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											103	65	43
Other Operations [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											(108)	(102)	(154)
Excluded realized gain (loss), after-tax [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											(218)	(337)	(214)
Gain (loss) on early extinguishment of debt, after-tax [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											(3)	(41)
Income (loss) from reserve changes (net of related amortization) on business sold through reinsurance, after-tax [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations												2	2
Benefit ratio unlocking, after-tax [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											129	$ 28	$ (29)
Net Impact From the Tax Cuts And Jobs Act [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											1,322
Impairment of intangibles, after-tax [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations											$ (905)

[1] Fourth quarter 2017 results include a goodwill impairment charge and the impacts of remeasuring our existing deferred tax balances for the impact of the Tax Act as disclosed elsewhere herein