Allowance for Loan and Lease Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 41,685	$ 38,715
Charge-offs	(10,658)	(3,064)
Recoveries	1,215	1,240
Provision	6,331	637
Ending Balance	38,573	37,528
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	13,099	11,388
Charge-offs	(6,917)	(538)
Recoveries	199	781
Provision	5,252	(2,332)
Ending Balance	11,633	9,299
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	14,152	14,473
Charge-offs	(923)	(1,243)
Recoveries	780	186
Provision	(999)	1,774
Ending Balance	13,010	15,190
Agricultural
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,992	2,138
Charge-offs	(1,511)	(23)
Recoveries	2	12
Provision	1,088	68
Ending Balance	2,571	2,195
Residential Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,720	3,543
Charge-offs	(149)	(265)
Recoveries	26	7
Provision	74	(19)
Ending Balance	3,671	3,266
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,722	7,173
Charge-offs	(1,158)	(995)
Recoveries	208	254
Provision	604	1,146
Ending Balance	7,376	7,578
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	0	0
Charge-offs	0	0
Recoveries	0	0
Provision	312	0
Ending Balance	$ 312	$ 0