Segment Information (Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total assets	$ 212,045	$ 211,425
Separate account assets	110,156	105,346
Separate account liabilities	110,156	105,346
Annuities
Segment Reporting Information [Line Items]
Total assets	149,920	146,224
Separate account assets	105,140	100,209
Separate account liabilities	105,140	100,209
Life
Segment Reporting Information [Line Items]
Total assets	13,044	12,296
Separate account assets	1,915	1,671
Separate account liabilities	1,915	1,671
Run-off
Segment Reporting Information [Line Items]
Total assets	36,719	40,575
Separate account assets	3,101	3,466
Separate account liabilities	3,101	3,466
Corporate & Other
Segment Reporting Information [Line Items]
Total assets	12,362	12,330
Separate account assets	0	0
Separate account liabilities	$ 0	$ 0