Fair Value of Financial Instruments Fair Value of Financial Instruments - Quantitative Estimates for Level 3 Liabilities (Details) (Level 3, USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
EIA/VED Embedded Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Embedded derivatives	$ 166.9	$ 153.9
Fair Value Inputs, CSA Rate	3.19%	3.08%
GMAB/GMWB Embedded Derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Embedded derivatives	$ 8.2	$ 6.4
Mortality rate	105.00%	105.00%
Fair Value Inputs, CSA Rate	3.19%	3.08%
Minimum | EIA/VED Embedded Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap curve	0.31%	0.24%
Mortality rate	97.00%	97.00%
Lapse rate	0.04%	0.04%
Minimum | GMAB/GMWB Embedded Derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap curve	0.22%	0.21%
Lapse rate	0.00%	0.00%
Volatility surface	8.58%	9.89%
Maximum | EIA/VED Embedded Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap curve	2.27%	2.55%
Mortality rate	105.00%	105.00%
Lapse rate	46.44%	46.44%
Maximum | GMAB/GMWB Embedded Derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap curve	2.44%	2.76%
Lapse rate	40.00%	40.00%
Volatility surface	50.72%	67.34%