Derivative Instruments (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Derivative
Number of Hedging instruments	0
Cash Flow Hedge
Derivative
Notional Amount	$ 0	$ 0	$ 0
Derivatives designated as hedging instruments
Derivative
Notional Amount		205,500,000
Derivative Assets		2,300,000
Derivative Liabilities		100,000
Derivatives designated as hedging instruments | Deposits and borrowings
Derivative
Derivative Assets		1,100,000
Derivatives designated as hedging instruments | Interest Rate Swaps
Derivative
Notional Amount	0
Derivatives designated as hedging instruments | Fair Value Hedge | Interest Rate Swaps
Derivative
Mark-to-market asset		1,100,000
Net interest receivable		1,200,000
Derivatives designated as hedging instruments | Fair Value Hedge | Interest Rate Swaps | Long-term and subordinated debt
Derivative
Notional Amount		205,500,000
Derivative Assets		2,300,000
Derivative Liabilities		100,000
Derivatives not designated as hedging instruments
Derivative
Notional Amount	3,591,300,000	2,719,100,000
Derivative Assets	53,100,000	66,800,000
Derivative Liabilities	51,000,000	65,900,000
Derivatives not designated as hedging instruments | Option contracts
Derivative
Derivative Assets	500,000	700,000
Derivatives not designated as hedging instruments | Interest Rate Contracts
Derivative
Notional Amount	3,082,900,000	2,487,700,000
Derivative Assets	48,300,000	64,600,000
Derivative Liabilities	47,300,000	64,600,000
Derivatives not designated as hedging instruments | Interest Rate Contracts | Options purchased
Derivative
Notional Amount	2,000,000	2,000,000
Derivative Assets	500,000	200,000
Derivative Liabilities	500,000	200,000
Derivatives not designated as hedging instruments | Interest Rate Contracts | Options written
Derivative
Notional Amount	2,000,000	2,000,000
Derivatives not designated as hedging instruments | Interest Rate Swaps
Derivative
Notional Amount	2,818,400,000	2,243,600,000
Derivative Assets	46,800,000	64,200,000
Derivative Liabilities	45,800,000	64,200,000
Derivatives not designated as hedging instruments | Interest Rate Caps, Floors and Collars
Derivative
Notional Amount	260,500,000	240,100,000
Derivative Assets	1,000,000	200,000
Derivative Liabilities	1,000,000	200,000
Derivatives not designated as hedging instruments | Spot and forward contracts
Derivative
Notional Amount	492,800,000	231,400,000
Derivative Assets	4,200,000	1,500,000
Derivative Liabilities	3,600,000	1,300,000
Derivatives not designated as hedging instruments | Foreign exchange contracts
Derivative
Notional Amount	508,400,000	231,400,000
Derivative Assets	4,300,000	1,500,000
Derivative Liabilities	3,700,000	1,300,000
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options purchased
Derivative
Notional Amount	7,800,000
Derivatives not designated as hedging instruments | Foreign exchange contracts | Options written
Derivative
Notional Amount	7,800,000
Derivative Assets	100,000
Derivative Liabilities	$ 100,000