Derivative Instruments (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Derivatives designated as hedging instruments
Derivative
Notional Amount	$ 205,900,000	$ 207,400,000
Derivative Assets	8,100,000	9,800,000
Derivatives designated as hedging instruments | Deposits and borrowings
Derivative
Derivative Assets	7,100,000	8,800,000
Derivatives designated as hedging instruments | Fair Value Hedge | Interest Rate Swaps
Derivative
Mark-to-market asset	7,100,000	8,800,000
Net interest receivable	1,000,000	1,000,000
Derivatives designated as hedging instruments | Fair Value Hedge | Interest Rate Swaps | Long-term and subordinated debt
Derivative
Notional Amount	205,900,000	207,400,000
Derivative Assets	8,100,000	9,800,000
Derivatives not designated as hedging instruments
Derivative
Notional Amount	2,088,600,000	1,957,000,000
Derivative Assets	51,900,000	54,500,000
Derivative Liabilities	51,700,000	55,000,000
Derivatives not designated as hedging instruments | Interest Rate Contracts
Derivative
Notional Amount	1,799,300,000	1,753,200,000
Derivative Assets	48,900,000	51,700,000
Derivative Liabilities	49,400,000	52,900,000
Derivatives not designated as hedging instruments | Interest Rate Swaps
Derivative
Notional Amount	1,551,400,000	1,482,100,000
Derivative Assets	48,600,000	51,300,000
Derivative Liabilities	49,100,000	52,500,000
Derivatives not designated as hedging instruments | Interest Rate Caps, Floors and Collars
Derivative
Notional Amount	243,900,000	267,100,000
Derivative Assets	100,000	300,000
Derivative Liabilities	100,000	300,000
Derivatives not designated as hedging instruments | Options purchased
Derivative
Notional Amount	2,000,000	2,000,000
Derivative Assets	200,000	100,000
Derivative Liabilities	200,000	100,000
Derivatives not designated as hedging instruments | Options written
Derivative
Notional Amount	2,000,000	2,000,000
Derivatives not designated as hedging instruments | Option contracts
Derivative
Derivative Assets	200,000	700,000
Derivatives not designated as hedging instruments | Foreign Exchange Contracts
Derivative
Notional Amount	289,300,000	203,800,000
Derivative Assets	2,800,000	2,100,000
Derivative Liabilities	2,300,000	2,100,000
Derivatives not designated as hedging instruments | Spot and forward contracts
Derivative
Notional Amount	277,700,000	203,800,000
Derivative Assets	2,700,000	2,100,000
Derivative Liabilities	2,200,000	2,100,000
Derivatives not designated as hedging instruments | Foreign exchange options purchased
Derivative
Notional Amount	5,800,000
Derivatives not designated as hedging instruments | Foreign exchange options written
Derivative
Notional Amount	5,800,000
Derivative Assets	100,000
Derivative Liabilities	$ 100,000