Recorded Investment in Nonperforming Loans by Class of Loans (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2012
Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Nonaccrual Loans $ 7,992 $ 7,401
Loans 90+ Days Past Due Still Accruing 99 363
Total Nonperforming Loans 9,569 11,515
Residential
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Nonaccrual Loans 2,698 2,281
Loans 90+ Days Past Due Still Accruing 67 143
Total Nonperforming Loans 7,117 7,308
Land
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Nonaccrual Loans 4 5
Loans 90+ Days Past Due Still Accruing 0 38
Total Nonperforming Loans 305 528
Construction
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Nonaccrual Loans 394 247
Loans 90+ Days Past Due Still Accruing 0 0
Total Nonperforming Loans 254 247
Commercial Real Estate
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Nonaccrual Loans 2,986 2,853
Loans 90+ Days Past Due Still Accruing 0 0
Total Nonperforming Loans 687 1,934
Commercial Business
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Nonaccrual Loans 1,809 1,928
Loans 90+ Days Past Due Still Accruing 0 0
Total Nonperforming Loans 25 256
Home Equity and Second Mortgage
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Nonaccrual Loans 101 87
Loans 90+ Days Past Due Still Accruing 0 159
Total Nonperforming Loans 793 876
Other Consumer
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Nonaccrual Loans 0 0
Loans 90+ Days Past Due Still Accruing 32 23
Total Nonperforming Loans 388 366
Nonperforming Financing Receivable
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total Nonperforming Loans 8,091 7,764
Nonperforming Financing Receivable | Residential
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total Nonperforming Loans 2,765 2,424
Nonperforming Financing Receivable | Land
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total Nonperforming Loans 4 43
Nonperforming Financing Receivable | Construction
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total Nonperforming Loans 394 247
Nonperforming Financing Receivable | Commercial Real Estate
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total Nonperforming Loans 2,986 2,853
Nonperforming Financing Receivable | Commercial Business
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total Nonperforming Loans 1,809 1,928
Nonperforming Financing Receivable | Home Equity and Second Mortgage
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total Nonperforming Loans 101 246
Nonperforming Financing Receivable | Other Consumer
    
Financing Receivable, Recorded Investment, Past Due [Line Items]    
Total Nonperforming Loans $ 32 $ 23