Reserves for Future Policy Benefits (Details) - Annuitization Benefit - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning Balance	$ 713	$ 322
Incurred	14	23
Paid	19	18
Change in unrealized investment gains and losses	(40)	(9)
Ending Balance	668	318
Movement in Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable [Roll Forward]
Beginning Balance	26	28
Incurred	9	(5)
Paid	0	0
Ending Balance	$ 35	$ 23