Derivative Financial Instruments (Details 2) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Derivatives, fair value disclosures
Total derivative instruments, assets	$ 821.3	$ 661.8
Total derivative instruments, liabilities	1,263.9	1,207.3
Fair value of embedded derivative liabilities reported with contractholder funds	210.3	176.4
Derivatives designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, assets	120.7	88.8
Total derivative instruments, liabilities	308.7	263.0
Derivatives not designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, assets	700.6	573.0
Total derivative instruments, liabilities	955.2	944.3
Interest rate contracts | Derivatives designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, assets	15.7	8.8
Total derivative instruments, liabilities	162.2	193.9
Interest rate contracts | Derivatives not designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, assets	597.8	508.7
Total derivative instruments, liabilities	314.1	321.4
Foreign exchange contracts | Derivatives designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, assets	105.0	80.0
Total derivative instruments, liabilities	146.5	69.1
Foreign exchange contracts | Derivatives not designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, assets	17.2	20.8
Total derivative instruments, liabilities	63.8	40.1
Equity contracts | Derivatives not designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, assets	72.5	30.2
Total derivative instruments, liabilities	91.7	131.7
Credit contracts | Derivatives not designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, assets	13.1	13.3
Total derivative instruments, liabilities	38.7	35.6
Other contracts | Derivatives not designated as hedging instrument
Derivatives, fair value disclosures
Total derivative instruments, liabilities	$ 446.9	$ 415.5