Guarantees (Details) (USD $)	Sep. 30, 2013 Y	Dec. 31, 2012
Guarantor Obligations [Line Items]
RPA's, minimum in years	4
RPA's, maximum in years	10
Notional amount of underlying interest rate swaps associated with risk participation agreements	$ 753,432,000	$ 554,418,000
Financial Standby Letter Of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, net liability	4,600,000
Guaranteed maximum potential future payments	347,300,000
Risk Participation Agreement [Member] | Indirect Guarantee Of Indebtedness [Member]
Guarantor Obligations [Line Items]
Notional amount of underlying interest rate swaps associated with risk participation agreements	44,700,000
Not Designated as Hedging Instrument [Member] | Risk Participation Agreement [Member] | Indirect Guarantee Of Indebtedness [Member]
Guarantor Obligations [Line Items]
Derivative Liabilities	$ 88,000