Allowance for Credit Losses, Loan Portfolio Allocated by Management's Internal Risk Ratings (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 1,226,695	$ 1,246,902	$ 1,158,283
Loans outstanding rated doubtful or loss	0	0	0
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	360,893	350,548	321,161
Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	318,823	311,992	277,631
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	32,681	32,680	32,036
Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	145,419	140,257	111,660
Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	40,141	42,042	49,094
Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	181,725	221,032	200,034
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	142,115	143,293	160,066
Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	4,898	5,058	6,601
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,170,557	1,189,106	1,073,246
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	336,525	326,037	283,721
Pass [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	308,475	299,642	250,827
Pass [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	26,472	26,445	23,876
Pass [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	142,951	137,998	109,453
Pass [Member] | Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	38,870	40,866	47,468
Pass [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	177,245	216,164	193,600
Pass [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	135,375	137,217	157,953
Pass [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	4,644	4,737	6,348
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	33,926	36,314	61,631
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	15,273	15,528	29,510
Special Mention [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	3,799	6,605	22,541
Special Mention [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	6,209	6,235	3,217
Special Mention [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,376	1,192	1,454
Special Mention [Member] | Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	0	0
Special Mention [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	980	1,168	3,295
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	6,289	5,586	1,614
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	22,212	21,482	23,406
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	9,095	8,983	7,930
Substandard [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	6,549	5,745	4,263
Substandard [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	0	4,943
Substandard [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,092	1,067	753
Substandard [Member] | Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,271	1,176	1,626
Substandard [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	3,500	3,700	3,139
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	451	490	499
Substandard [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 254	$ 321	$ 253