Segment Information (Reconciliation of Assets From Segments to Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	$ 261,627	$ 251,908
Parent Company [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	21,020	19,998
Annuities Segment [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	133,817	130,641
Retirement Plan Services Segment [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	34,344	32,649
Life Insurance Segment [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	76,083	71,062
Group Protection Segment [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	4,007	4,182
Other Operations [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	$ 13,376	$ 13,374