Guarantees (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Derivative Liabilities	$ 5,979	$ 13,339
Notional amount of underlying interest rate swaps associated with risk participation agreements	1,933,725	$ 1,904,093
Financial Standby Letter Of Credit [Member]
Guarantor Obligations [Line Items]
Standby letters of credit, net liability	2,100
Contractual amount of letters of credit, guaranteed maximum potential future payments	338,400
Risk Participation Agreement [Member] | Indirect Guarantee Of Indebtedness [Member]
Guarantor Obligations [Line Items]
Derivative Liabilities	129
Notional amount of underlying interest rate swaps associated with risk participation agreements	$ 74,900
Minimum [Member] | Risk Participation Agreement [Member]
Guarantor Obligations [Line Items]
Term, in years	3 years
Maximum [Member] | Risk Participation Agreement [Member]
Guarantor Obligations [Line Items]
Term, in years	11 years