Loans (Risk Category of Loans) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 999,989	$ 1,008,678
Loans Acquired With Deteriorated Credit Quality	10,184	10,877
Commercial and Industrial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	332,987	336,307
Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	499,717	489,796
Agricultural Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	167,285	182,575
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	924,199	931,366
Loans Acquired With Deteriorated Credit Quality	318	319
Pass [Member] | Commercial and Industrial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	304,247	307,997
Pass [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	458,396	446,639
Pass [Member] | Agricultural Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	161,556	176,730
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	39,129	38,634
Loans Acquired With Deteriorated Credit Quality	3,406	3,220
Special Mention [Member] | Commercial and Industrial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	14,732	14,441
Special Mention [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	21,617	21,338
Special Mention [Member] | Agricultural Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,780	2,855
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	36,661	38,678
Loans Acquired With Deteriorated Credit Quality	6,460	7,338
Substandard [Member] | Commercial and Industrial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	14,008	13,869
Substandard [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	19,704	21,819
Substandard [Member] | Agricultural Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,949	2,990
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	0	0
Loans Acquired With Deteriorated Credit Quality	0	0
Doubtful [Member] | Commercial and Industrial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	0	0
Doubtful [Member] | Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	0	0
Doubtful [Member] | Agricultural Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 0	$ 0