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	3 Months Ended		12 Months Ended
	Sep. 30, 2014		Dec. 31, 2013
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	$ 1,944.2		$ 2,192.4
NAR before Reinsurance	76.6		73.4
NAR after Reinsurance	19.3		13.7
Average Attained Age of Annuitant	65 years		64 years
Less: General account value with GMDB	276.4		294.7
Subtotal separate account liabilities with GMDB	1,667.8		1,897.7
Separate account liabilities without GMDB	148.5		155.0
Total separate account liabilities	1,816.3		2,052.7
GMIB	324.3	[1]	385.7	[1]
GMDB return of premium [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	646.8		728.8
NAR before Reinsurance	1.5		1.8
NAR after Reinsurance	1.5		1.8
Average Attained Age of Annuitant	63 years		63 years
GMDB step up [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	1,241.7		1,401.0
NAR before Reinsurance	70.1		66.7
NAR after Reinsurance	12.8		7.0
Average Attained Age of Annuitant	64 years		63 years
GMDB earnings enhancement benefit (EEB) [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	30.9		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 [Member]
Net Amount at Risk by Product and Guarantee [Line Items]
Account Value	24.8		26.7
NAR before Reinsurance	5.0		4.8
NAR after Reinsurance	$ 5.0		$ 4.8
Average Attained Age of Annuitant	68 years		68 years

[1] .