Reinsurance - Account Value, Net Amount at Risk and Contractholders for GMDB Business (Details) - Variable Annuity [Member] - Guaranteed Minimum Death Benefit [Member] $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Contractholders	Dec. 31, 2015 USD ($) Contractholders
Guaranteed Minimum Death Benefits Account Value, Net Amount at Risk And Average Age Table [Line Items]
Account value	$ 10,650	$ 11,355
Net amount at risk	$ 2,458	$ 2,870
Average attained age of contractholders (weighted by exposure)	75 years	74 years
Number of contractholders | Contractholders	285,000	324,000