Derivative Instruments (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Derivative
Number of Hedging instruments	0
Cash Flow Hedge
Derivative
Notional Amount		$ 0
Derivatives designated as hedging instruments
Derivative
Notional Amount	0	205,500,000
Derivative Assets	0	2,300,000
Derivative Liabilities	0	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	0	205,500,000
Derivative Assets	0	2,300,000
Derivative Liabilities	0	100,000
Derivatives not designated as hedging instruments
Derivative
Notional Amount	3,347,800,000	2,719,100,000
Derivative Assets	48,200,000	66,800,000
Derivative Liabilities	46,900,000	65,900,000
Derivatives not designated as hedging instruments | Option contracts
Derivative
Derivative Assets	600,000	700,000
Derivatives not designated as hedging instruments | Interest Rate Contracts
Derivative
Notional Amount	2,926,500,000	2,487,700,000
Derivative Assets	45,600,000	64,600,000
Derivative Liabilities	44,400,000	64,600,000
Derivatives not designated as hedging instruments | Interest Rate Swaps
Derivative
Notional Amount	2,691,900,000	2,243,600,000
Derivative Assets	44,900,000	64,200,000
Derivative Liabilities	43,700,000	64,200,000
Derivatives not designated as hedging instruments | Interest Rate Caps, Floors and Collars
Derivative
Notional Amount	230,600,000	240,100,000
Derivative Assets	300,000	200,000
Derivative Liabilities	300,000	200,000
Derivatives not designated as hedging instruments | Spot and forward contracts
Derivative
Notional Amount	421,300,000	231,400,000
Derivative Assets	2,000,000	1,500,000
Derivative Liabilities	2,500,000	1,300,000
Derivatives not designated as hedging instruments | Foreign exchange options written | Options purchased
Derivative
Notional Amount	2,000,000	2,000,000
Derivative Assets	400,000	200,000
Derivative Liabilities	400,000	200,000
Derivatives not designated as hedging instruments | Foreign exchange options written | Options written
Derivative
Notional Amount	$ 2,000,000	$ 2,000,000