Segment Information (Reconciliation of Assets From Segments to Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total assets	$ 281,763	$ 261,627
Parent Company [Member]
Segment Reporting Information [Line Items]
Total assets	23,716	21,020
Annuities Segment [Member]
Segment Reporting Information [Line Items]
Total assets	144,721	133,817
Retirement Plan Services Segment [Member]
Segment Reporting Information [Line Items]
Total assets	37,072	34,344
Life Insurance Segment [Member]
Segment Reporting Information [Line Items]
Total assets	81,381	76,083
Group Protection Segment [Member]
Segment Reporting Information [Line Items]
Total assets	4,033	4,007
Other Operations [Member]
Segment Reporting Information [Line Items]
Total assets	$ 14,556	$ 13,376