Loans and Allowance for Loan Losses (Components of loans receivable) (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2012
Jun. 30, 2012
Dec. 31, 2011
Sep. 30, 2011
Jun. 30, 2011
Dec. 31, 2010
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment $ 490,898   $ 482,547      
Individually evaluated for impairment 20,807   32,135      
Percentage of loans receivable 100.00%   100.00%      
Total loans receivable 511,705   514,682      
Allowance for loan losses (9,088) (10,233) (12,690) (14,367) (13,687) (12,455)
Deferred loan fees, net of direct origination costs 235   260      
Loans receivable, net 502,852   502,252      
Weighted average interest rate 5.43%   5.69%      
Commercial
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 107,755   101,810      
Individually evaluated for impairment 7,448   8,585      
Percentage of loans receivable 22.50%   21.40%      
Total loans receivable 115,203   110,395      
Allowance for loan losses (3,073) (2,429) (2,817) (2,751) (2,782) (2,925)
Commercial real estate
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 170,007   156,668      
Individually evaluated for impairment 4,958   10,918      
Percentage of loans receivable 34.20%   32.60%      
Total loans receivable 174,965   167,586      
Allowance for loan losses (2,728) (4,032) (4,880) (5,563) (5,086) (3,655)
Commercial construction
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 2,573   5,588      
Individually evaluated for impairment 0   747      
Percentage of loans receivable 0.50%   1.20%      
Total loans receivable 2,573   6,335      
Allowance for loan losses (67) (94) (500) (722) (728) (540)
Land and land development loans
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 30,276   33,326      
Individually evaluated for impairment 3,538   5,173      
Percentage of loans receivable 6.60%   7.50%      
Total loans receivable 33,814   38,499      
Allowance for loan losses (1,654) (1,565) (2,273) (2,099) (2,046) (2,408)
Agriculture
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 85,627   78,893      
Individually evaluated for impairment 2,224   2,423      
Percentage of loans receivable 17.20%   15.80%      
Total loans receivable 87,851   81,316      
Allowance for loan losses (187) (207) (172) (802) (909) (779)
Multifamily
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 17,849   26,038      
Individually evaluated for impairment 0   0      
Percentage of loans receivable 3.50%   5.10%      
Total loans receivable 17,849   26,038      
Allowance for loan losses (56) (57) (91) (95) (90) (83)
Residential real estate
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 56,926   54,848      
Individually evaluated for impairment 2,441   4,013      
Percentage of loans receivable 11.60%   11.40%      
Total loans receivable 59,367   58,861      
Allowance for loan losses (1,042) (1,601) (1,566) (1,643) (1,324) (1,252)
Residential construction
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 532   2,742      
Individually evaluated for impairment 0   0      
Percentage of loans receivable 0.10%   0.50%      
Total loans receivable 532   2,742      
Allowance for loan losses (13) (4) (59) (80) (119) (65)
Consumer
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 9,526   11,571      
Individually evaluated for impairment 198   276      
Percentage of loans receivable 1.90%   2.30%      
Total loans receivable 9,724   11,847      
Allowance for loan losses (198) (201) (295) (584) (577) (613)
Municipal
           
Accounts, Notes, Loans and Financing Receivable [Line Items]            
Collectively evaluated for impairment 9,827   11,063      
Individually evaluated for impairment 0   0      
Percentage of loans receivable 1.90%   2.20%      
Total loans receivable 9,827   11,063      
Allowance for loan losses $ (70) $ (43) $ (37) $ (28) $ (26) $ (135)