Allowance for Loan Losses, Aging Analysis of Loan Portfolio by the Time Past Due (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	$ 157	$ 1,238	$ 4,228
90 Days or More and Still Accruing	0	0	0
Nonaccrual	5,752	4,228	4,664
Total Past Due	5,909	5,466	8,892
Current	1,204,118	1,157,612	1,168,613
Total Loans	1,210,027	1,163,078	1,177,505
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	0	0
90 Days or More and Still Accruing	0	0	0
Nonaccrual	0	1,354	811
Total Past Due	0	1,354	811
Current	335,664	304,350	300,107
Total Loans	335,664	305,704	300,918
Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	0	0
90 Days or More and Still Accruing	0	0	0
Nonaccrual	2,551	954	1,413
Total Past Due	2,551	954	1,413
Current	291,313	279,185	282,736
Total Loans	293,864	280,139	284,149
Real Estate Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	0	0
90 Days or More and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Past Due	0	0	0
Current	32,701	29,607	28,979
Total Loans	32,701	29,607	28,979
Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	108	0
90 Days or More and Still Accruing	0	0	0
Nonaccrual	279	284	347
Total Past Due	279	392	347
Current	137,185	107,029	103,783
Total Loans	137,464	107,421	104,130
Home Equity Lines and Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	101	566	359
90 Days or More and Still Accruing	0	0	0
Nonaccrual	528	194	190
Total Past Due	629	760	549
Current	43,361	50,196	51,902
Total Loans	43,990	50,956	52,451
Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	284	3,854
90 Days or More and Still Accruing	0	0	0
Nonaccrual	2,374	1,202	1,531
Total Past Due	2,374	1,486	5,385
Current	190,679	215,741	214,285
Total Loans	193,053	217,227	219,670
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	179	0
90 Days or More and Still Accruing	0	0	0
Nonaccrual	0	217	348
Total Past Due	0	396	348
Current	167,777	164,693	179,981
Total Loans	167,777	165,089	180,329
Consumer & Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	56	101	15
90 Days or More and Still Accruing	0	0	0
Nonaccrual	20	23	24
Total Past Due	76	124	39
Current	5,438	6,811	6,840
Total Loans	$ 5,514	$ 6,935	$ 6,879