Separate Accounts, Death Benefits and Other Insurance Benefit Features and Embedded Product Derivatives - GMDB and GMIB Benefits by Type (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	$ 2,081.8	$ 2,192.4
NAR before Reinsurance	69.0	73.4
NAR after Reinsurance	11.9	13.7
Average Attained Age of Annuitant	65 years	64 years
Less: General account value with GMDB	284.3	294.7
Subtotal separate account liabilities with GMDB	1,797.5	1,897.7
Separate account liabilities without GMDB	153.5	155.0
Total separate account liabilities	1,951.0	2,052.7
GMIB	354.7	385.7
GMDB return of premium
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	691.4	728.8
NAR before Reinsurance	1.4	1.8
NAR after Reinsurance	1.4	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	1,330.2	1,401.0
NAR before Reinsurance	63.0	66.7
NAR after Reinsurance	5.9	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	33.8	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	26.4	26.7
NAR before Reinsurance	4.6	4.8
NAR after Reinsurance	$ 4.6	$ 4.8
Average Attained Age of Annuitant	68 years	68 years