Reinsurance - Guaranteed Minimum Death Benefits Account Value, Net Amount at Risk and Contractholders (Details) - Variable Annuity [Member] - Guaranteed Minimum Death Benefit [Member] Contractholders in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 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	$ 10,977	$ 11,355
Net amount at risk	$ 2,854	$ 2,870
Number of contractholders | Contractholders	318,000	324,000