Segment Information (Reconciliation of Assets From Segments to Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	$ 251,937	$ 253,377
Parent Company [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	20,027	21,999
Annuities Segment [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	130,641	130,316
Retirement Plan Services Segment [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	32,649	33,678
Life Segment [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	71,062	70,493
Group Protection Segment [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	4,182	4,238
Other Operations [Member]
Schedule Of Segment Reporting And Reconcilliation [Line Items]
Total assets	$ 13,403	$ 14,652