Past Due and Non-Accrual Loans by Class (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 718	$ 1,663
60-89 Days Past Due	444	185
Greater than 90 Days Past Due	1,731	1,128
Total Past Due	2,893	2,976
Past Due 90 Days or More and Still Accruing
Loans on Non-Accrual	3,009	2,933
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	94	840
60-89 Days Past Due	331
Greater than 90 Days Past Due	818	740
Total Past Due	1,243	1,580
Past Due 90 Days or More and Still Accruing
Loans on Non-Accrual	1,558	1,879
Residential real estate | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	347	562
60-89 Days Past Due	70
Greater than 90 Days Past Due	735	184
Total Past Due	1,152	746
Past Due 90 Days or More and Still Accruing
Loans on Non-Accrual	939	670
Residential real estate | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	139	128
60-89 Days Past Due	42
Greater than 90 Days Past Due		204
Total Past Due	181	332
Past Due 90 Days or More and Still Accruing
Loans on Non-Accrual	103	230
Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	138	111
60-89 Days Past Due		183
Greater than 90 Days Past Due	178
Total Past Due	316	294
Past Due 90 Days or More and Still Accruing
Loans on Non-Accrual	409	154
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due		22
60-89 Days Past Due	1	2
Total Past Due	1	24
Past Due 90 Days or More and Still Accruing