Allowance for Credit Losses, Aging Analysis of Loan Portfolio by the Time Past Due (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	$ 169	$ 547	$ 3,003
90 Days or More and Still Accruing	0	0	0
Nonaccrual	10,427	9,298	3,015
Total Past Due	10,596	9,845	6,018
Current	1,284,460	1,237,057	1,197,976
Total Loans	1,295,056	1,246,902	1,203,994
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	150	105
90 Days or More and Still Accruing	0	0	0
Nonaccrual	2,873	0	0
Total Past Due	2,873	150	105
Current	390,286	350,398	324,690
Total Loans	393,159	350,548	324,795
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	5,817	5,423	1,512
Total Past Due	5,817	5,423	1,512
Current	306,771	306,569	284,118
Total Loans	312,588	311,992	285,630
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	32,718	32,680	36,033
Total Loans	32,718	32,680	36,033
Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	23	11
90 Days or More and Still Accruing	0	0	0
Nonaccrual	202	445	452
Total Past Due	202	468	463
Current	136,271	139,789	122,590
Total Loans	136,473	140,257	123,053
Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	152	70	132
90 Days or More and Still Accruing	0	0	0
Nonaccrual	243	213	346
Total Past Due	395	283	478
Current	37,103	41,759	45,806
Total Loans	37,498	42,042	46,284
Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	0	2,384
90 Days or More and Still Accruing	0	0	0
Nonaccrual	997	3,198	587
Total Past Due	997	3,198	2,971
Current	213,763	217,834	207,809
Total Loans	214,760	221,032	210,780
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	1	293	327
90 Days or More and Still Accruing	0	0	0
Nonaccrual	277	0	97
Total Past Due	278	293	424
Current	159,369	143,000	171,197
Total Loans	159,647	143,293	171,621
Consumer & Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	16	11	44
90 Days or More and Still Accruing	0	0	0
Nonaccrual	18	19	21
Total Past Due	34	30	65
Current	5,512	5,028	5,733
Total Loans	5,546	5,058	5,798
Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0
90 Days or More and Still Accruing	0
Nonaccrual	0
Total Past Due	0
Current	2,667
Total Loans	$ 2,667