Allowance for Credit Losses, Aging Analysis of Loan Portfolio by the Time Past Due (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	$ 821	$ 547	$ 157
90 Days or More and Still Accruing	0	0	0
Nonaccrual	3,783	9,298	5,752
Total Past Due	4,604	9,845	5,909
Current	1,293,207	1,237,057	1,204,118
Total Loans	1,297,811	1,246,902	1,210,027
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	592	150	0
90 Days or More and Still Accruing	0	0	0
Nonaccrual	176	0	0
Total Past Due	768	150	0
Current	400,858	350,398	335,664
Total Loans	401,626	350,548	335,664
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	849	5,423	2,551
Total Past Due	849	5,423	2,551
Current	310,552	306,569	291,313
Total Loans	311,401	311,992	293,864
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	27,099	32,680	32,701
Total Loans	27,099	32,680	32,701
Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	23	0
90 Days or More and Still Accruing	0	0	0
Nonaccrual	455	445	279
Total Past Due	455	468	279
Current	143,122	139,789	137,185
Total Loans	143,577	140,257	137,464
Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	121	70	101
90 Days or More and Still Accruing	0	0	0
Nonaccrual	243	213	528
Total Past Due	364	283	629
Current	36,796	41,759	43,361
Total Loans	37,160	42,042	43,990
Agricultural [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	99	3,198	2,374
Total Past Due	99	3,198	2,374
Current	221,470	217,834	190,679
Total Loans	221,569	221,032	193,053
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	0	293	0
90 Days or More and Still Accruing	0	0	0
Nonaccrual	1,944	0	0
Total Past Due	1,944	293	0
Current	143,849	143,000	167,777
Total Loans	145,793	143,293	167,777
Consumer & Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 89 Days Past Due	108	11	56
90 Days or More and Still Accruing	0	0	0
Nonaccrual	17	19	20
Total Past Due	125	30	76
Current	4,938	5,028	5,438
Total Loans	5,063	5,058	5,514
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	4,523
Total Loans	$ 4,523	$ 0	$ 0