Allowance for Loan and Lease Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 48,685	$ 41,449
Charge-offs	(1,605)	(2,004)
Recoveries	591	738
Provision	2,067	1,671
Ending Balance	49,738	41,854
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	16,095	11,909
Charge-offs	(98)	(274)
Recoveries	176	320
Provision	201	(267)
Ending Balance	16,374	11,688
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	19,532	15,898
Charge-offs	(312)	(333)
Recoveries	146	126
Provision	1,129	944
Ending Balance	20,495	16,635
Agricultural
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,887	3,295
Charge-offs	0	(276)
Recoveries	3	22
Provision	138	175
Ending Balance	4,028	3,216
Residential real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,934	3,741
Charge-offs	(37)	(58)
Recoveries	20	37
Provision	(66)	25
Ending Balance	1,851	3,745
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,237	6,606
Charge-offs	(1,158)	(1,063)
Recoveries	246	233
Provision	665	794
Ending Balance	6,990	6,570
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	0	0
Charge-offs	0	0
Recoveries	0	0
Provision	0	0
Ending Balance	$ 0	$ 0