Employee Benefit Arrangements - Net Actuarial (Gains) Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss recognition	$ (15)	$ (55)	$ 63
Discount Rate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss recognition	(196)	(69)	133
Asset Returns
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss recognition	142	(24)	(123)
Mortality Table Assumptions
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss recognition	14	22	32
Demographic Data and other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net (gain) loss recognition	$ 25	$ 16	$ 21