Allowance for Loan and Lease Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 39,362	$ 43,271	$ 36,808	$ 42,693
Charge-offs	(2,254)	(8,183)	(3,862)	(18,206)
Recoveries	1,331	1,669	3,139	2,261
Provision	3,000	3,845	5,354	13,854
Ending Balance	41,439	40,602	41,439	40,602
Agricultural Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,847	1,982	1,763	2,147
Charge-offs	0	(95)	0	(167)
Recoveries	3	0	81	0
Provision	152	95	158	2
Ending Balance	2,002	1,982	2,002	1,982
Residential Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,540	2,336	3,001	2,381
Charge-offs	(213)	(616)	(276)	(1,229)
Recoveries	33	23	66	25
Provision	539	765	1,108	1,331
Ending Balance	3,899	2,508	3,899	2,508
Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	7,555	6,502	6,874	6,315
Charge-offs	(1,028)	(1,375)	(1,785)	(2,222)
Recoveries	230	167	464	314
Provision	1,436	1,352	2,640	2,239
Ending Balance	8,193	6,646	8,193	6,646
Finance Leases Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1	20	2	9
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	0	(13)	(1)	(2)
Ending Balance	1	7	1	7
Unallocated Financing Receivables
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	0	0	0	1,000
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	0	0	0	(1,000)
Ending Balance	0	0	0	0
Commercial | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	11,019	10,644	10,547	10,525
Charge-offs	(205)	(617)	(707)	(2,004)
Recoveries	216	324	249	393
Provision	(743)	(254)	198	1,183
Ending Balance	10,287	10,097	10,287	10,097
Commercial Real Estate | Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	15,400	21,787	14,621	20,316
Charge-offs	(808)	(5,480)	(1,094)	(12,584)
Recoveries	849	1,155	2,279	1,529
Provision	1,616	1,900	1,251	10,101
Ending Balance	$ 17,057	$ 19,362	$ 17,057	$ 19,362