Loans and Allowance for Loan Losses (Components of allowance for loan losses) (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
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance $ 9,088 $ 10,233 $ 12,690 $ 14,367 $ 13,687 $ 12,455
Individually evaluated allowance 3,213   6,250      
Collectively evaluated allowance 5,875   6,440      
Commercial
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 3,073 2,429 2,817 2,751 2,782 2,925
Individually evaluated allowance 1,732   1,300      
Collectively evaluated allowance 1,341   1,517      
Commercial real estate
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 2,728 4,032 4,880 5,563 5,086 3,655
Individually evaluated allowance 604   2,804      
Collectively evaluated allowance 2,124   2,076      
Commercial construction
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 67 94 500 722 728 540
Individually evaluated allowance 0   252      
Collectively evaluated allowance 67   248      
Land and land development loans
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 1,654 1,565 2,273 2,099 2,046 2,408
Individually evaluated allowance 345   728      
Collectively evaluated allowance 1,309   1,545      
Agriculture
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 187 207 172 802 909 779
Individually evaluated allowance 10   32      
Collectively evaluated allowance 177   140      
Multifamily
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 56 57 91 95 90 83
Individually evaluated allowance 0   0      
Collectively evaluated allowance 56   91      
Residential real estate
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 1,042 1,601 1,566 1,643 1,324 1,252
Individually evaluated allowance 405   939      
Collectively evaluated allowance 637   627      
Residential construction
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 13 4 59 80 119 65
Individually evaluated allowance 0   0      
Collectively evaluated allowance 13   59      
Consumer
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 198 201 295 584 577 613
Individually evaluated allowance 117   195      
Collectively evaluated allowance 81   100      
Municipal
           
Financing Receivable, Allowance for Credit Losses [Line Items]            
Total allowance 70 43 37 28 26 135
Individually evaluated allowance 0   0      
Collectively evaluated allowance $ 70   $ 37