Loans and Allowance for Loan Losses (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	$ 1,060,685,000	$ 982,710,000
Net deferred loan fees, premiums and discounts	(237,000)	(420,000)
Allowance for loan losses	13,682,000	13,249,000	11,776,000	11,120,000
Net loans	1,046,766,000	969,041,000
Loans held for sale	1,958,000	514,000
Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	21,627,000	25,321,000
Farm loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	110,158,000	109,376,000
1-4 Family residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	179,886,000	184,158,000
Multifamily residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	53,129,000	50,174,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	380,173,000	357,726,000
Debt coverage ratio	1.20x
Amortization period of loans	twenty years
Commercial real estate | Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan To Value Ratio	65.00%
Commercial real estate | Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan To Value Ratio	80.00%
Loans secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	744,973,000	726,755,000
Agricultural loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	68,225,000	64,055,000
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	223,633,000	168,227,000
Loan To Value Ratio	80.00%
Amortization period of loans	seven years
Loans Receivable, Time Period	one year
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	15,118,000	14,579,000
Allowance for loan losses	386,000	377,000	403,000	378,000
All other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	8,736,000	9,094,000
Agricultural and Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	178,500,000	173,500,000
Increase (Decrease) in Accounts and Notes Receivable	5,000,000
Loan To Value Ratio	65.00%
Amortization period of loans	twenty five years
Loans Receivable, Time Period	one year
Other Grain Farming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	155,100,000	147,100,000
Increase (Decrease) in Accounts and Notes Receivable	8,000,000
Motels and Hotels Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	56,500,000
General Merchandise Stores [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	46,200,000
Non-residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	96,500,000
Residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	65,800,000
Commercial/Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	10,914,000	10,646,000	9,301,000	8,791,000
Agriculture/Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,360,000	533,000	558,000	546,000
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	790,000	771,000	726,000	636,000
Loan To Value Ratio	80.00%
Amortization period of loans	twenty five years
Balloon period	five years
Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 232,000	$ 922,000	$ 788,000	$ 769,000