Loans and Allowance for Credit Losses - Summary of outstanding loans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 597,694,000	$ 572,442,000
% of Total Loans	100.00%	100.00%
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	$ 417,000	$ 146,000
Loans and Leases Receivable, Gross	598,111,000	572,588,000
Loans, allowance for credit losses	(9,610,000)	(8,308,000)
Loans and Leases Receivable, Net Amount	588,501,000	564,280,000
Investments securing FHLB advances, amortized cost	470,080,000
Salaries and employee benefits deferred as loan origination costs	2,056,000	1,657,000	$ 1,373,000
Owner occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 168,910,000	$ 176,804,000
% of Total Loans	28.20%	30.90%
Agricultural land and production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 30,472,000	$ 39,140,000
% of Total Loans	5.10%	6.80%
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 132,669,000	$ 128,147,000
% of Total Loans	22.20%	22.30%
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 102,197,000	$ 89,007,000
% of Total Loans	17.10%	15.50%
Real estate construction and other land loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 38,685,000	$ 38,923,000
% of Total Loans	6.50%	6.80%
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 117,244,000	$ 106,788,000
% of Total Loans	19.60%	18.70%
Agricultural real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 74,867,000	$ 57,501,000
% of Total Loans	12.50%	10.00%
Other real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 10,520,000	$ 6,611,000
% of Total Loans	1.80%	1.20%
Equity loans and lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 42,296,000	$ 47,575,000
% of Total Loans	7.10%	8.30%
Consumer and installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 12,503,000	$ 10,093,000
% of Total Loans	2.10%	1.80%
Real Estate Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 410,226,000	$ 386,627,000
% of Total Loans	68.60%	67.60%
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 54,799,000	$ 57,668,000
% of Total Loans	9.20%	10.10%
Small Business Administration Programs [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Real Estate and Commercial	$ 10,704,000	$ 8,782,000
Federal Home Loan Bank Advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Pledged as Collateral	215,223,000
Remaining borrowing capacity	308,356,000
Securities Pledged as Collateral | Federal Home Loan Bank Advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investments securing FHLB advances, amortized cost	750,000	1,256,000
Investments securing FLHB advances, market value	$ 825,000	$ 1,364,000