Segment Information - Reconciliation of Segment Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net investment income	$ 4,004	$ 3,269	$ 2,914
Operating Segments | Retirement Services
Segment Reporting Information [Line Items]
Net investment income	4,188	3,241	2,953
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
Net investment income	44	182	77
Non-operating adjustments
Segment Reporting Information [Line Items]
Reinsurance Embedded Derivative Gain (Loss)	(301)	(191)	(189)
Income (Loss) from Variable Interest Entities, Net	(37)	(77)	(1)
Alternative Income Gain (Loss)	34	20	39
Other Adjustment to Net Investment Income	$ 76	$ 94	$ 35