Allowance for Loan and Lease Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 40,892	$ 37,623	$ 41,685	$ 38,715
Charge-offs	(2,649)	(2,513)	(14,707)	(8,350)
Recoveries	902	1,052	3,085	3,298
Provision	2,553	5,149	11,635	7,648
Ending Balance	41,698	41,311	41,698	41,311
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	11,927	9,436	13,099	11,388
Charge-offs	(875)	(163)	(7,940)	(1,422)
Recoveries	145	78	552	983
Provision	158	3,745	5,644	2,147
Ending Balance	11,355	13,096	11,355	13,096
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	14,680	13,671	14,152	14,473
Charge-offs	(295)	(630)	(1,379)	(2,561)
Recoveries	539	514	1,833	1,279
Provision	1,221	488	1,539	852
Ending Balance	16,145	14,043	16,145	14,043
Agricultural
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,788	3,055	2,992	2,138
Charge-offs	(338)	0	(1,974)	(23)
Recoveries	5	1	9	100
Provision	661	(240)	2,089	601
Ending Balance	3,116	2,816	3,116	2,816
Residential real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,815	3,580	3,720	3,543
Charge-offs	(21)	(450)	(225)	(856)
Recoveries	29	76	85	102
Provision	(200)	331	43	748
Ending Balance	3,623	3,537	3,623	3,537
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,516	7,881	7,722	7,173
Charge-offs	(1,120)	(1,270)	(3,189)	(3,488)
Recoveries	184	383	606	834
Provision	673	825	2,114	3,300
Ending Balance	7,253	7,819	7,253	7,819
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	166	0	0	0
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	40	0	206	0
Ending Balance	$ 206	$ 0	$ 206	$ 0