Reinsurance - Future Policy Benefits for GMDB Business (Details) - Variable Annuity [Member] - Guaranteed Minimum Death Benefit [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Activity in future policy benefits reserves for GMDB business [Line Items]
Future Policy Benefit Reserve, beginning balance, gross	$ 1,224	$ 1,252
Beginning balance, unpaid claims, gross	16	18
Less: Reinsurance and other amounts recoverable	1,129	1,164
Future Policy Benefit Reserve, beginning balance, net	111	106
Add: Incurred benefits	0	4
Less: Paid benefits / (recoveries)	(1)	(1)
Future Policy Benefit Reserve, ending balance, net	112	111
Ending balance, unpaid claims, gross	17	16
Add: Reinsurance and other amounts recoverable	1,027	1,129
Future Policy Benefit Reserve, ending balance, gross	$ 1,122	$ 1,224