Loans and allowance for loan losses (5) (Details) (USD $)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2011
Information concerning Troubled Debt Restructurings [Abstract]          
Total $ 6,654,698 $ 6,852,606 $ 41,684,985 $ 10,468,544  
Information about TDRs Identified during the period [Abstract]          
Number of loans 14 7 73 13 31
Financing Receivable Modifications Pre Modification Recorded Investment During period 6,654,698 6,852,606 21,199,955 10,468,544 21,966,175
Financing Receivable Modifications Post Modification Recorded Investment During period 6,654,698 6,852,606 21,199,955 10,468,544 21,966,175
Defaults on TDRs [Abstract]          
Number of loans 3 7 51 13 15
Recorded investment 620,998 8,363,526 9,181,811 14,016,012 15,294,960
Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period 17,949 1,227,522 3,534,841 1,268,868  
Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 4,875,753 3,837,577 22,097,446 5,213,033  
Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 1,144,351 3,015,029 19,587,539 5,255,511  
Commercial [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 39,769 2,655,029 9,876,951 5,495,511  
Information about TDRs Identified during the period [Abstract]          
Number of loans 1 2 12 7 11
Financing Receivable Modifications Pre Modification Recorded Investment During period 39,769 2,655,029 3,938,672 5,495,511 6,604,400
Financing Receivable Modifications Post Modification Recorded Investment During period 39,769 2,655,029 3,938,672 5,495,511 6,604,400
Defaults on TDRs [Abstract]          
Number of loans 1 4 17 10 8
Recorded investment 39,769 5,822,810 4,703,352 11,475,296 11,389,291
Commercial [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period 0 823,522 996,602 864,868  
Commercial [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 0 0 5,165,826 600,000  
Commercial [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 39,769 2,655,029 4,711,125 4,895,511  
Residential [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     191,544 0  
Information about TDRs Identified during the period [Abstract]          
Number of loans 0   3    
Financing Receivable Modifications Pre Modification Recorded Investment During period 0 0 191,544   0
Financing Receivable Modifications Post Modification Recorded Investment During period 0 0 191,544 0 0
Defaults on TDRs [Abstract]          
Number of loans 0   3   0
Recorded investment 0   191,544   0
Residential [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period     0 0  
Residential [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     0 0  
Residential [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     191,544 0  
Total construction and land development [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 39,769 2,655,029 10,068,495 5,495,511  
Information about TDRs Identified during the period [Abstract]          
Number of loans 1 2 15 7 11
Financing Receivable Modifications Pre Modification Recorded Investment During period 39,769 2,655,029 4,130,216 5,495,511 6,604,400
Financing Receivable Modifications Post Modification Recorded Investment During period 39,769 2,655,029 4,130,216 5,495,511 6,604,400
Defaults on TDRs [Abstract]          
Number of loans 1 4 20 10 8
Recorded investment 39,769 5,822,810 4,894,896 11,475,296 11,389,291
Total construction and land development [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period 0 823,522 996,602 864,868  
Total construction and land development [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 0 0 5,165,826 600,000  
Total construction and land development [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 39,769 2,655,029 4,902,669 4,895,511  
Farmland [Member]
         
Information about TDRs Identified during the period [Abstract]          
Financing Receivable Modifications Pre Modification Recorded Investment During period 0 0 0    
Financing Receivable Modifications Post Modification Recorded Investment During period 0 0 0 0 0
Defaults on TDRs [Abstract]          
Number of loans 0   0    
Recorded investment 0   0    
Commercial real estate - owner occupied [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 0 0 10,385,569 0  
Information about TDRs Identified during the period [Abstract]          
Number of loans 0   1 0 9
Financing Receivable Modifications Pre Modification Recorded Investment During period 0 0 1,388,851   9,748,062
Financing Receivable Modifications Post Modification Recorded Investment During period 0 0 1,388,851 0 9,748,062
Defaults on TDRs [Abstract]          
Number of loans 0 1 3 1 2
Recorded investment 0 2,180,716 496,933 2,180,716 2,202,688
Commercial real estate - owner occupied [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period     1,025,656 0  
Commercial real estate - owner occupied [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 0 0 5,886,028 0  
Commercial real estate - owner occupied [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 0 0 4,499,541 0  
Commercial real estate - non-owner occupied [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 4,737,776 0 13,760,683 775,456  
Information about TDRs Identified during the period [Abstract]          
Number of loans 7   9 1 5
Financing Receivable Modifications Pre Modification Recorded Investment During period 4,737,776 0 9,665,791 775,456 4,031,868
Financing Receivable Modifications Post Modification Recorded Investment During period 4,737,776 0 9,665,791 775,456 4,031,868
Defaults on TDRs [Abstract]          
Number of loans 1   1    
Recorded investment 461,265   461,265   0
Commercial real estate - non-owner occupied [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period 0   753,170 0  
Commercial real estate - non-owner occupied [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 4,276,511 0 7,759,407 775,456  
Commercial real estate - non-owner occupied [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 461,265 0 6,001,276 0  
Multifamily [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 634,594 0 1,210,273 0  
Information about TDRs Identified during the period [Abstract]          
Number of loans 1   1    
Financing Receivable Modifications Pre Modification Recorded Investment During period 634,594 0 634,594   0
Financing Receivable Modifications Post Modification Recorded Investment During period 634,594 0 634,594 0 0
Defaults on TDRs [Abstract]          
Number of loans 1   4   2
Recorded investment 461,265   958,198   2,202,688
Multifamily [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period 0 0 0 0  
Multifamily [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 0 0 1,210,273 0  
Multifamily [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 0 0 0 0  
Total commercial real estate [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 5,372,370 0 25,356,525 775,456  
Information about TDRs Identified during the period [Abstract]          
Number of loans 8 0 11 1 14
Financing Receivable Modifications Pre Modification Recorded Investment During period 5,372,370 0 11,689,236 775,456 13,779,930
Financing Receivable Modifications Post Modification Recorded Investment During period 5,372,370 0 11,689,236 775,456 13,779,930
Defaults on TDRs [Abstract]          
Number of loans   1   1  
Recorded investment   2,180,716   2,180,716  
Total commercial real estate [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period 0 0 1,778,826 0  
Total commercial real estate [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 4,276,511 0 14,855,708 775,456  
Total commercial real estate [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 461,265 0 10,500,817 0  
Home equity lines [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     349,192 0  
Information about TDRs Identified during the period [Abstract]          
Number of loans 0   1    
Financing Receivable Modifications Pre Modification Recorded Investment During period 0 0 349,192 0 0
Financing Receivable Modifications Post Modification Recorded Investment During period 0 0 349,192 0 0
Defaults on TDRs [Abstract]          
Number of loans 0   1    
Recorded investment 0   349,192    
Home equity lines [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period     96,569 0  
Home equity lines [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     0 0  
Home equity lines [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     349,192 0  
Secured by 1-4 family residential, secured by first deeds of trust [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 1,042,595 3,837,577 5,384,930 3,837,577  
Information about TDRs Identified during the period [Abstract]          
Number of loans 4 3 39 3 2
Financing Receivable Modifications Pre Modification Recorded Investment During period 1,042,595 3,837,577 4,505,468 3,837,577 1,422,772
Financing Receivable Modifications Post Modification Recorded Investment During period 1,042,595 3,837,577 4,505,468 3,837,577 1,422,772
Defaults on TDRs [Abstract]          
Number of loans 0   20   2
Recorded investment 0   2,459,862   1,422,772
Secured by 1-4 family residential, secured by first deeds of trust [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period 17,949 404,000 579,444 404,000  
Secured by 1-4 family residential, secured by first deeds of trust [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 599,242 3,837,577 2,069,732 3,837,577  
Secured by 1-4 family residential, secured by first deeds of trust [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 443,353 0 3,315,198 0  
Secured by 1-4 family residential, secured by second deeds of trust [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     69,815 0  
Information about TDRs Identified during the period [Abstract]          
Number of loans 0   1    
Financing Receivable Modifications Pre Modification Recorded Investment During period 0 0 69,815 0 0
Financing Receivable Modifications Post Modification Recorded Investment During period 0 0 69,815 0 0
Defaults on TDRs [Abstract]          
Number of loans 0   1    
Recorded investment 0   69,815   0
Secured by 1-4 family residential, secured by second deeds of trust [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period     0 0  
Secured by 1-4 family residential, secured by second deeds of trust [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     0 0  
Secured by 1-4 family residential, secured by second deeds of trust [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total     69,815 0  
Total consumer real estate [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 1,042,595 3,837,577 5,803,937 3,837,577  
Information about TDRs Identified during the period [Abstract]          
Number of loans 4 3 41 3 2
Financing Receivable Modifications Pre Modification Recorded Investment During period 1,042,595 3,837,577 4,924,475 3,837,577 1,422,772
Financing Receivable Modifications Post Modification Recorded Investment During period 1,042,595 3,837,577 4,924,475 3,837,577 1,422,772
Defaults on TDRs [Abstract]          
Number of loans 0   22   2
Recorded investment 0   2,878,869   1,422,772
Total consumer real estate [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period 17,949 404,000 676,013 404,000  
Total consumer real estate [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 599,242 3,837,577 2,069,732 3,837,577  
Total consumer real estate [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 443,353 0 3,734,205 0  
Commercial and industrial loans (except those secured by real estate) [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 199,964 360,000 456,028 360,000  
Information about TDRs Identified during the period [Abstract]          
Number of loans 1 2 6 2 3
Financing Receivable Modifications Pre Modification Recorded Investment During period 199,964 360,000 456,028 360,000 159,073
Financing Receivable Modifications Post Modification Recorded Investment During period 199,964 360,000 456,028 360,000 159,073
Defaults on TDRs [Abstract]          
Number of loans 1 2 5 2 2
Recorded investment 119,964 360,000 449,848 360,000 151,790
Commercial and industrial loans (except those secured by real estate) [Member] | Specific Valuation Allowance [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Financing Receivable Modifications Related Allowance During Period   0 83,400 0  
Commercial and industrial loans (except those secured by real estate) [Member] | Performing [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 0 0 6,180 0  
Commercial and industrial loans (except those secured by real estate) [Member] | Nonaccrual [Member]
         
Information concerning Troubled Debt Restructurings [Abstract]          
Total 199,964 360,000 449,848 360,000  
Consumer and other [Member]
         
Information about TDRs Identified during the period [Abstract]          
Number of loans 0   0   1
Financing Receivable Modifications Pre Modification Recorded Investment During period 0   0   128,419
Financing Receivable Modifications Post Modification Recorded Investment During period 0   0   128,419
Defaults on TDRs [Abstract]          
Number of loans 0   0   1
Recorded investment $ 0   $ 0   $ 128,419