Reinsurance Reinsurance (Net Amount at Risk and 100 Percent Mortality) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Guaranteed Minimum Benefits [Line Items]
Average attained age of all policyholders under all benefits reinsured, years	70 years
GLB
Guaranteed Minimum Benefits [Line Items]
Net Amount at Risk	$ 800	$ 733
GMDB
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	3.75%
Net Amount at Risk	$ 341	364
Mortality percentage according to Annuity 2000 mortality table	100.00%
GMDB with Both Risk(GMDB and GLB) [Member]
Guaranteed Minimum Benefits [Line Items]
Net Amount at Risk	$ 88	89
GLB with Both Risk(GLB and GMDB) [Member]
Guaranteed Minimum Benefits [Line Items]
Net Amount at Risk	$ 464	$ 422
Minimum | GLB
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	4.25%
Minimum | GMDB
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	3.25%
Minimum | GLB with Both Risk(GLB and GMDB) [Member]
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	4.25%
Maximum | GLB
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	4.75%
Maximum | GLB with Both Risk(GLB and GMDB) [Member]
Guaranteed Minimum Benefits [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	4.75%