Aging of Recorded Investment in Loans (Detail) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2013
Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]    
30-59 Days Past Due $ 6,311 $ 6,711
60-89 Days Past Due 956 1,003
Over 90 Days Past Due 2,393 2,326
Total Past Due 9,660 10,040
Current 279,349 276,196
Recorded investment in loans 289,009 286,236
Residential
    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
30-59 Days Past Due 4,871 4,085
60-89 Days Past Due 615 871
Over 90 Days Past Due 1,453 1,644
Total Past Due 6,939 6,600
Current 101,310 102,003
Recorded investment in loans 108,249 108,603
Land
    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
30-59 Days Past Due 277 343
60-89 Days Past Due 51 0
Over 90 Days Past Due 123 119
Total Past Due 451 462
Current 9,759 9,195
Recorded investment in loans 10,210 9,657
Construction
    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
30-59 Days Past Due 0 171
60-89 Days Past Due 0 0
Over 90 Days Past Due 109 113
Total Past Due 109 284
Current 11,974 11,479
Recorded investment in loans 12,083 11,763
Commercial Real Estate
    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
30-59 Days Past Due 94 360
60-89 Days Past Due 71 0
Over 90 Days Past Due 122 335
Total Past Due 287 695
Current 70,182 68,207
Recorded investment in loans 70,469 68,902
Commercial Business
    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
30-59 Days Past Due 0 36
60-89 Days Past Due 0 0
Over 90 Days Past Due 237 0
Total Past Due 237 36
Current 21,203 18,619
Recorded investment in loans 21,440 18,655
Home Equity and Second Mortgage
    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
30-59 Days Past Due 728 1,206
60-89 Days Past Due 14 102
Over 90 Days Past Due 340 97
Total Past Due 1,082 1,405
Current 33,095 35,881
Recorded investment in loans 34,177 37,286
Other Consumer
    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
30-59 Days Past Due 341 510
60-89 Days Past Due 205 30
Over 90 Days Past Due 9 18
Total Past Due 555 558
Current 31,826 30,812
Recorded investment in loans $ 32,381 $ 31,370