Commitments and Contingent Liabilities (Details) - USD ($) $ in Thousands		12 Months Ended
	Aug. 24, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Minimum future rental payments:
2016		$ 8,891
2017		8,184
2018		7,355
2019		6,514
2020		5,138
Thereafter		13,474
Total minimum payments		49,556
Operating Leases, Rent Expense, Sublease Rentals		992	$ 1,100	$ 756
Operating Leases, Rent Expense, Net		8,700	7,400	$ 8,300
Sale Leaseback Transaction, Date	August 24, 2016
Sale Leaseback Transaction, Monthly Rental Payments		12
Sale Leaseback Transaction, Deferred Gain, Gross	$ 742
Sale Leaseback Transaction, Deferred Gain, Net		713
Commitments to Extend Credit [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability		2,170,000	1,930,000
Standby Letters of Credit [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability		49,700	38,700
Commercial Letter of Credit and other off-balance sheet liabilities [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability		3,400	$ 5,000
Branch consolidation [Member]
Loss Contingencies [Line Items]
Restructuring and Related Cost, Incurred Cost		883
Minimum future rental payments:
Increase (Decrease) in Restructuring Reserve		$ 849