11. Separate Accounts Death Benefits, Other Insurance Benefit Features and Embedded Product Derivatives (Details 2) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Account Value	$ 2,880.4	$ 2,906.0
Net Amount at Risk After Reinsurance	45.8	130.8
Average Attained Age Of Annuitant	63 years	63 years
Less: General account value with GMDB	427.1	444.1
Subtotal separate account liabilities with GMDB	2,453.3	2,461.9
Separate account liabilities without GMDB	942.1	1,355.0
Total separate account liabilities	3,395.4	3,816.9
GMIB(1) at end of period	427.3	442.1
Return of premium
Account Value	819.9	839.6
Net Amount at Risk After Reinsurance	8.0	22.5
Average Attained Age Of Annuitant	62 years	61 years
Step up
Account Value	1,994.0	1,999.5
Net Amount at Risk After Reinsurance	30.2	99.1
Average Attained Age Of Annuitant	62 years	62 years
Earnings enhancement benefit ("EEB")
Account Value	39.0	39.8
Net Amount at Risk After Reinsurance	0.1	0.4
Average Attained Age Of Annuitant	62 years	62 years
Greater of annual step up and roll up
Account Value	27.5	27.1
Net Amount at Risk After Reinsurance	$ 7.5	$ 8.8
Average Attained Age Of Annuitant	62 years	66 years