Reinsurance - Guaranteed Minimum Death Benefits Account Value, Net Amount at Risk and Contractholders (Details) (Variable Annuity [Member], Guaranteed Minimum Death Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 Contractholders	Dec. 31, 2013 Contractholders
Variable Annuity [Member] | Guaranteed Minimum Death Benefit [Member]
Guaranteed Minimum Death Benefits Account Value, Net Amount at Risk And Average Age Table [Line Items]
Account value	$ 13,078	$ 14,062
Net amount at risk	$ 2,763	$ 3,023
Average attained age of contractholders (weighted by exposure)	73 years	73 years
Number of contractholders	354,000	390,000