Reinsurance - Guaranteed Minimum Death Benefits Account Value, Net Amount at Risk and Contractholders (Details) (Variable Annuity [Member], Guaranteed Minimum Death Benefit [Member], USD $) In Billions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015 Contractholders	Dec. 31, 2014 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	$ 12.9	$ 13.1
Net amount at risk	$ 2.7	$ 2.8
Number of contractholders	346,000	354,000