Guaranteed Benefit Features - Net Amount at Risk of Minimum Guaranteed Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
GMDB
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 1,706	$ 1,674
Net amount at risk, net of reinsurance	$ 48	$ 59
Weighted average attained age	68 years	68 years
GMAB/GMWB
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 26	$ 30
Net amount at risk, net of reinsurance	$ 1	$ 1
Weighted average attained age	71 years	68 years
GMIB
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 290	$ 304
Net amount at risk, net of reinsurance	$ 37	$ 60
Weighted average attained age	62 years	62 years
GMWBL
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 286	$ 283
Net amount at risk, net of reinsurance	$ 3	$ 9
Weighted average attained age	71 years	70 years
Held for sale | GMDB
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 28,701	$ 30,839
Net amount at risk, net of reinsurance	$ 3,929	$ 5,504
Weighted average attained age	71 years	71 years
Held for sale | GMAB/GMWB
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 525	$ 534
Net amount at risk, net of reinsurance	$ 11	$ 14
Weighted average attained age	74 years	73 years
Held for sale | GMIB
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 7,247	$ 9,807
Net amount at risk, net of reinsurance	$ 1,656	$ 2,886
Weighted average attained age	64 years	63 years
Held for sale | GMWBL
Net Amount at Risk by Product and Guarantee [Line Items]
Separate account value	$ 13,587	$ 13,311
Net amount at risk, net of reinsurance	$ 1,573	$ 2,201
Weighted average attained age	69 years	68 years