Allowance for Loan Losses, Loan Portfolio Allocated by Management's Internal Credit Ratings (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Loans:	$ 1,246,902	$ 1,163,078
Loans outstanding rated doubtful or loss	0	0
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	350,548	305,704
Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	311,992	280,139
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	32,680	29,607
Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	140,257	107,421
Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	42,042	50,956
Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	221,032	217,227
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	143,293	165,089
Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	5,058	6,935
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	1,189,106	1,069,406
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	326,037	265,201
Pass [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	299,642	254,181
Pass [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	26,445	21,428
Pass [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	137,998	104,609
Pass [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	40,866	49,631
Pass [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	216,164	209,555
Pass [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	137,217	158,273
Pass [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	4,737	6,528
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	36,314	50,866
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	15,528	15,186
Special Mention [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	6,605	21,657
Special Mention [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	6,235	3,217
Special Mention [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	1,192	1,483
Special Mention [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	0	0
Special Mention [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	1,168	4,083
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	5,586	5,240
Special Mention [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	0	0
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	21,482	42,806
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	8,983	25,317
Substandard [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	5,745	4,301
Substandard [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:		4,962
Substandard [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	1,067	1,329
Substandard [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	1,176	1,325
Substandard [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	3,700	3,589
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	490	1,576
Substandard [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans:	$ 321	$ 407