Segment Information (Reconciliation Of Revenue From Segments To Consolidated) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total revenues	$ 4,531	$ 4,264	$ 4,020	$ 3,609	$ 3,669	$ 3,511	$ 3,577	$ 3,500	$ 16,424	$ 14,257	$ 13,330
Annuities Segment [Member]
Segment Reporting Information [Line Items]
Total revenues									4,383	4,378	4,033
Retirement Plan Services Segment [Member]
Segment Reporting Information [Line Items]
Total revenues									1,178	1,165	1,103
Life Insurance Segment [Member]
Segment Reporting Information [Line Items]
Total revenues									6,922	6,558	6,246
Group Protection Segment [Member]
Segment Reporting Information [Line Items]
Total revenues									3,757	2,201	2,130
Other Operations [Member]
Segment Reporting Information [Line Items]
Total revenues									235	287	332
Excluded realized gain (loss), pre-tax [Member]
Segment Reporting Information [Line Items]
Total revenues									(46)	(336)	(518)
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
Amortization Of DFEL Associated With Benefit Ratio Unlocking, Pre-Tax [Member]
Segment Reporting Information [Line Items]
Total revenues									$ (5)	$ 3	$ 1