Allowance for Loan Losses, Aging Analysis of Loan Portfolio by the Time Past Due (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	$ 547,000	$ 1,238,000
90 Days or More and Still Accruing	0	0
Nonaccrual	9,298,000	4,228,000
Total Past Due	9,845,000	5,466,000
Current	1,237,057,000	1,157,612,000
Total Loans	1,246,902,000	1,163,078,000
Interest income forgone on nonaccrual loans	209,000	385,000	356,000
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	150,000	0
90 Days or More and Still Accruing	0	0
Nonaccrual	0	1,354,000
Total Past Due	150,000	1,354,000
Current	350,398,000	304,350,000
Total Loans	350,548,000	305,704,000
Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	0
90 Days or More and Still Accruing	0	0
Nonaccrual	5,423,000	954,000
Total Past Due	5,423,000	954,000
Current	306,569,000	279,185,000
Total Loans	311,992,000	280,139,000
Real Estate Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	0
90 Days or More and Still Accruing	0	0
Nonaccrual	0	0
Total Past Due	0	0
Current	32,680,000	29,607,000
Total Loans	32,680,000	29,607,000
Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	23,000	108,000
90 Days or More and Still Accruing	0	0
Nonaccrual	445,000	284,000
Total Past Due	468,000	392,000
Current	139,789,000	107,029,000
Total Loans	140,257,000	107,421,000
Home Equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	70,000	566,000
90 Days or More and Still Accruing	0	0
Nonaccrual	213,000	194,000
Total Past Due	283,000	760,000
Current	41,759,000	50,196,000
Total Loans	42,042,000	50,956,000
Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	284,000
90 Days or More and Still Accruing	0	0
Nonaccrual	3,198,000	1,202,000
Total Past Due	3,198,000	1,486,000
Current	217,834,000	215,741,000
Total Loans	221,032,000	217,227,000
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	293,000	179,000
90 Days or More and Still Accruing	0	0
Nonaccrual	0	217,000
Total Past Due	293,000	396,000
Current	143,000,000	164,693,000
Total Loans	143,293,000	165,089,000
Consumer & Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	11,000	101,000
90 Days or More and Still Accruing	0	0
Nonaccrual	19,000	23,000
Total Past Due	30,000	124,000
Current	5,028,000	6,811,000
Total Loans	$ 5,058,000	$ 6,935,000