Allowance for Loan Losses, Loan Portfolio Allocated by Management's Internal Credit Ratings (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 1,210,027	$ 1,163,078	$ 1,177,505
Loans outstanding rated doubtful or loss	0	0	0
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	335,664	305,704	300,918
Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	293,864	280,139	284,149
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	32,701	29,607	28,979
Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	137,464	107,421	104,130
Home Equity Lines and Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	43,990	50,956	52,451
Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	193,053	217,227	219,670
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	167,777	165,089	180,329
Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,514	6,935	6,879
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,142,846	1,069,406	1,075,164
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	313,441	265,201	260,662
Pass [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	273,823	254,181	259,428
Pass [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	24,856	21,428	20,781
Pass [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	135,473	104,609	101,230
Pass [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	41,975	49,631	51,559
Pass [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	186,398	209,555	202,323
Pass [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	161,685	158,273	172,702
Pass [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,195	6,528	6,479
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	38,159	50,866	57,773
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	15,910	15,186	15,482
Special Mention [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,887	21,657	19,315
Special Mention [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	3,217	3,217	3,217
Special Mention [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,211	1,483	1,503
Special Mention [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	0	0
Special Mention [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,300	4,083	12,285
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,634	5,240	5,971
Special Mention [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	0	0
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	29,022	42,806	44,568
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	6,313	25,317	24,774
Substandard [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	10,154	4,301	5,406
Substandard [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	4,628	4,962	4,981
Substandard [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	780	1,329	1,397
Substandard [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,015	1,325	892
Substandard [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	4,355	3,589	5,062
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	458	1,576	1,656
Substandard [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 319	$ 407	$ 400