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	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
EIA/VED Embedded Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Embedded derivatives	$ 69.0	$ 51.2
GMAB/GMWB Embedded Derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Embedded derivatives	$ 3.6	$ 28.3
Income Approach Valuation Technique | EIA/VED Embedded Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortality rate	75.00%	75.00%
Fair Value Inputs, CSA Rate	3.99%	4.47%
Income Approach Valuation Technique | GMAB/GMWB Embedded Derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Mortality rate	75.00%	75.00%
Fair Value Inputs, CSA Rate	3.99%	4.47%
Income Approach Valuation Technique | Minimum | EIA/VED Embedded Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap curve	0.22%	0.21%
Lapse rate	0.60%	1.00%
Income Approach Valuation Technique | Minimum | GMAB/GMWB Embedded Derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap curve	0.14%	0.36%
Lapse rate	0.00%	0.00%
Volatility surface	11.46%	11.67%
Income Approach Valuation Technique | Maximum | EIA/VED Embedded Derivative
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap curve	3.46%	2.50%
Lapse rate	35.00%	35.00%
Income Approach Valuation Technique | Maximum | GMAB/GMWB Embedded Derivatives
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Swap curve	3.88%	3.17%
Lapse rate	60.00%	60.00%
Volatility surface	51.22%	50.83%