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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations					$ 348	$ 439	$ 398	$ 329	$ 1,154	$ 1,514	$ 1,244
Income (loss) from discontinued operations, after-tax					1					1
Net income (loss)	$ 283	$ 227	$ 344	$ 300	$ 349	$ 439	$ 398	$ 329	1,154	1,515	1,244
Annuities Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations									996	925	750
Retirement Plan Services Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations									140	160	141
Life Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations									370	612	544
Group Protection Segment [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations									43	23	71
Other Operations [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations									(154)	(109)	(122)
Excluded realized gain (loss), after-tax [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations									(214)	(106)	(178)
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	2
Benefit ratio unlocking, after-tax [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Income (loss) from continuing operations									(29)	7	36
Parent Company [Member]
Reconciliation of Net Income (Loss) from Segments to Consolidated [Abstract]
Net income (loss)									$ 1,154	$ 1,515	$ 1,244