Segment Information (Reconciliation Of Revenue From Segments To Consolidated) (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
Segment Reporting Information [Line Items]
Total revenues	$ 3,669		$ 3,511	$ 3,577	$ 3,500	$ 3,255		$ 3,525	$ 3,307	$ 3,243	$ 14,257	$ 13,330	$ 13,572
Annuities Segment [Member]
Segment Reporting Information [Line Items]
Total revenues											4,378	4,033	4,120
Retirement Plan Services Segment [Member]
Segment Reporting Information [Line Items]
Total revenues											1,165	1,103	1,101
Life Insurance Segment [Member]
Segment Reporting Information [Line Items]
Total revenues											6,558	6,246	5,948
Group Protection Segment [Member]
Segment Reporting Information [Line Items]
Total revenues											2,201	2,130	2,357
Other Operations [Member]
Segment Reporting Information [Line Items]
Total revenues											287	332	374
Excluded realized gain (loss), pre-tax [Member]
Segment Reporting Information [Line Items]
Total revenues											(336)	(518)	(329)
Amortization of deferred gain arising from reserve changes on business sold through reinsurance, pre-tax [Member]
Segment Reporting Information [Line Items]
Total revenues											1	3	3
Amortization Of DFEL Associated With Benefit Ratio Unlocking, Pre-Tax [Member]
Segment Reporting Information [Line Items]
Total revenues											$ 3	$ 1	$ (2)

[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