Segments - Operating Revenues (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues	$ 2,186	$ 2,184	$ 2,191	$ 2,057	$ 2,324	$ 2,110	$ 2,088	$ 2,266	$ 8,618	$ 8,788	$ 8,716
Total operating revenues									8,046	8,479	8,237
Segment Reconciling Items
Segment Reporting Information [Line Items]
Total revenues									572	309	479
Net realized investment gains (losses) and related charges and adjustments									(100)	(112)	(121)
Gain (loss) on change in fair value of derivatives related to guaranteed benefits									52	9	(63)
Revenues related to business exited through reinsurance or divestment									122	96	26
Revenues attributable to noncontrolling interest									286	133	414
Other adjustments									212	183	223
Retirement | Operating Segments
Segment Reporting Information [Line Items]
Total operating revenues									2,538	3,257	2,994
Investment Management | Operating Segments
Segment Reporting Information [Line Items]
Total operating revenues									731	627	622
Investment Management | Intersegment
Segment Reporting Information [Line Items]
Total operating revenues									118	114	110
Individual Life | Operating Segments
Segment Reporting Information [Line Items]
Total operating revenues									2,563	2,528	2,617
Employee Benefits | Operating Segments
Segment Reporting Information [Line Items]
Total operating revenues									1,767	1,616	1,507
Corporate
Segment Reporting Information [Line Items]
Total operating revenues									$ 447	$ 451	$ 497