Guarantees (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Guarantor Obligations [Line Items]
Derivative Liabilities	$ 16,373	$ 8,074
Notional amount of underlying interest rate swaps associated with risk participation agreements	2,016,270	$ 1,963,178
Financial Standby Letter Of Credit [Member]
Guarantor Obligations [Line Items]
Standby letters of credit, net liability	2,300
Contractual amount of letters of credit, guaranteed maximum potential future payments	389,600
Risk Participation Agreement [Member] | Indirect Guarantee Of Indebtedness [Member]
Guarantor Obligations [Line Items]
Derivative Liabilities	91
Notional amount of underlying interest rate swaps associated with risk participation agreements	$ 103,900
Minimum [Member] | Risk Participation Agreement [Member]
Guarantor Obligations [Line Items]
Term, in years	2 years
Maximum [Member] | Risk Participation Agreement [Member]
Guarantor Obligations [Line Items]
Term, in years	11 years