Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014 item	Dec. 31, 2013 item
Derivative
Number of Hedging instruments	0	0
Derivatives not designated as hedging instruments
Derivative
Notional Amount	$ 3,947.4	$ 3,499.9
Derivative Assets	44.9	47.9
Derivative Liabilities	44.8	46.3
Derivatives not designated as hedging instruments | Equity Warrants
Derivative
Notional Amount	1.8
Derivative Assets	0.7
Derivatives not designated as hedging instruments | Option contracts
Derivative
Notional Amount	2.1	1.9
Derivative Assets	0.3	0.4
Derivatives not designated as hedging instruments | Interest Rate Contracts
Derivative
Notional Amount	3,285.9	3,024.0
Derivative Assets	38.9	43.8
Derivative Liabilities	38.9	42.8
Derivatives not designated as hedging instruments | Interest Rate Contracts | Options purchased | Purchase
Derivative
Notional Amount	0.2	1.5
Derivative Assets	0.1	0.6
Derivative Liabilities	0.2	0.6
Derivatives not designated as hedging instruments | Interest Rate Contracts | Options purchased | Sale
Derivative
Notional Amount	0.2	1.5
Derivatives not designated as hedging instruments | Interest Rate Swaps
Derivative
Notional Amount	2,975.3	2,769.4
Derivative Assets	37.9	42.7
Derivative Liabilities	37.8	41.7
Derivatives not designated as hedging instruments | Interest Rate Caps, Floors and Collars
Derivative
Notional Amount	310.2	251.6
Derivative Assets	0.9	0.5
Derivative Liabilities	0.9	0.5
Derivatives not designated as hedging instruments | Spot and forward contracts
Derivative
Notional Amount	651.6	461.4
Derivative Assets	4.8	3.5
Derivative Liabilities	5.7	3.3
Derivatives not designated as hedging instruments | Foreign exchange contracts
Derivative
Notional Amount	657.6	474.0
Derivative Assets	5.0	3.7
Derivative Liabilities	5.9	3.5
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options purchased | Purchase
Derivative
Notional Amount	3.0	6.3
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options purchased | Sale
Derivative
Notional Amount	3.0	6.3
Derivative Assets	0.2	0.2
Derivative Liabilities	$ 0.2	$ 0.2