Derivative Instruments (Details) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Derivatives designated as hedging instruments
Derivative
Notional Amount	$ 355.2	$ 365.9	$ 468.2
Derivative Assets	14.5	20.1	29.2
Derivatives designated as hedging instruments | Fair Value Hedge
Derivative
Net interest receivable	1.8	1.8	1.7
Derivatives designated as hedging instruments | Fair Value Hedge | Interest Rate Swaps
Derivative
Notional Amount	355.2	365.9	368.2
Derivative Assets	14.5	20.1	28.3
Mark-to-market asset	14.5	21.4
Net interest receivable	1.8	1.8	1.7
Cash collateral received from a counter party	1.8	3.1
Derivatives designated as hedging instruments | Fair Value Hedge | Interest Rate Swaps | Certificates of deposit
Derivative
Notional Amount		10.0	10.0
Derivative Assets		0.3	0.5
Derivatives designated as hedging instruments | Fair Value Hedge | Interest Rate Swaps | Long-term and subordinated debt
Derivative
Notional Amount	355.2	355.9	358.2
Derivative Assets	14.5	19.8	27.8
Derivatives designated as hedging instruments | Fair Value Hedge | Other assets
Derivative
Derivative Assets	14.5	20.1	28.3
Derivatives designated as hedging instruments | Cash Flow Hedge | Interest Rate Swaps
Derivative
Notional Amount			100.0
Derivative Assets			0.9
Mark-to-market asset			0.6
Net interest receivable			0.3
Derivatives designated as hedging instruments | Cash Flow Hedge | Interest Rate Swaps | U.S. Dollar LIBOR based loans
Derivative
Notional Amount			50.0
Derivative Assets			0.3
Derivatives designated as hedging instruments | Cash Flow Hedge | Interest Rate Swaps | Prime based loans
Derivative
Notional Amount			50.0
Derivative Assets			0.6
Derivatives designated as hedging instruments | Cash Flow Hedge | Accumulated other comprehensive income (loss)
Derivative
Net deferred gain related to terminated cash flow hedges	0.3	1.2	3.6
Derivatives designated as hedging instruments | Interest Rate Swaps
Derivative
Notional Amount	355.2	365.9	468.2
Derivatives designated as hedging instruments | Deposits and borrowings
Derivative
Derivative Assets			26.6
Derivatives not designated as hedging instruments
Derivative
Notional Amount	1,310.4	1,210.5	1,544.2
Derivative Assets	30.9	27.7	37.1
Derivative Liabilities	30.4	27.4	37.4
Derivatives not designated as hedging instruments | Interest Rate Contracts
Derivative
Notional Amount	1,190.7	1,132.3	1,162.5
Derivative Assets	29.2	26.4	29.5
Derivative Liabilities	29.5	26.4	30.1
Derivatives not designated as hedging instruments | Interest Rate Swaps
Derivative
Notional Amount	1,071.4	1,043.8	979.2
Derivative Assets	28.5	25.7	29.0
Derivative Liabilities	28.8	25.7	29.6
Derivatives not designated as hedging instruments | Interest Rate Caps, Floors and Collars
Derivative
Notional Amount	115.3	84.5	179.3
Derivative Assets	0.5	0.5	0.4
Derivative Liabilities	0.5	0.5	0.4
Derivatives not designated as hedging instruments | Options purchased
Derivative
Notional Amount	2.0	2.0	2.0
Derivative Assets	0.2	0.2	0.1
Derivative Liabilities	0.2	0.2	0.1
Derivatives not designated as hedging instruments | Options written
Derivative
Notional Amount	2.0	2.0	2.0
Derivatives not designated as hedging instruments | Option contracts
Derivative
Derivative Assets	0.5
Derivatives not designated as hedging instruments | Foreign Exchange Contracts
Derivative
Notional Amount	119.7	78.2	381.7
Derivative Assets	1.2	1.3	7.6
Derivative Liabilities	0.9	1.0	7.3
Derivatives not designated as hedging instruments | Spot and forward contracts
Derivative
Notional Amount	119.7	78.2	237.9
Derivative Assets	1.2	1.3	6.0
Derivative Liabilities	0.9	1.0	5.7
Derivatives not designated as hedging instruments | Foreign exchange options purchased
Derivative
Notional Amount			71.9
Derivative Assets			0.1
Derivative Liabilities			0.1
Derivatives not designated as hedging instruments | Foreign exchange options written
Derivative
Notional Amount			71.9
Derivative Assets			1.5
Derivative Liabilities			$ 1.5