Separate Accounts, Death Benefits and Other Insurance Benefit Features and Embedded Product Derivative - GMDB and GMIB Benefits by Type (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	$ 2,118.9		$ 2,192.4
NAR before Reinsurance	72.2		73.4
NAR after Reinsurance	13.4		13.7
Average Attained Age of Annuitant	65 years		64 years
Less: General account value with GMDB	289.8		294.7
Subtotal separate account liabilities with GMDB	1,829.1		1,897.7
Separate account liabilities without GMDB	150.2		155.0
Total separate account liabilities	1,979.3		2,052.7
GMIB	367.0	[1]	385.7	[1]
GMDB return of premium
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	704.2		728.8
NAR before Reinsurance	1.7		1.8
NAR after Reinsurance	1.7		1.8
Average Attained Age of Annuitant	63 years		63 years
GMDB step up
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	1,353.0		1,401.0
NAR before Reinsurance	65.7		66.7
NAR after Reinsurance	6.9		7.0
Average Attained Age of Annuitant	64 years		63 years
GMDB earnings enhancement benefit (“EEB”)
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	35.5		35.9
NAR before Reinsurance	0		0.1
NAR after Reinsurance	0		0.1
Average Attained Age of Annuitant	64 years		64 years
GMDB greater of annual step up and roll up
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	26.2		26.7
NAR before Reinsurance	4.8		4.8
NAR after Reinsurance	$ 4.8		$ 4.8
Average Attained Age of Annuitant	68 years		68 years

[1] Policies with a GMIB also have a GMDB, however these benefits are not additive. When a policy terminates due to death, any NAR related to GMIB is released. Similarly, when a policy goes into benefit status on a GMIB, its GMDB NAR is released.