Past Due Loan Trends for Corporation's Loans Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 -59 Days Past Due	$ 1,947	$ 3,736
60 - 89 Days Past Due	2,010	1,429
Greater Than 90 Days	6,994	8,879
Total Past Due	10,951	14,044
Current	112,348	113,752
Total loans	123,299	127,796
Commercial Portfolio Segment | Commercial Non Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 -59 Days Past Due	75	146
60 - 89 Days Past Due	64	110
Greater Than 90 Days	854	646
Total Past Due	993	902
Current	8,127	8,122
Total loans	9,120	9,024
Commercial Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 -59 Days Past Due	931	2,525
60 - 89 Days Past Due	1,459	482
Greater Than 90 Days	4,536	6,047
Total Past Due	6,926	9,054
Current	67,457	66,156
Total loans	74,383	75,210
Consumer Portfolio Segment | Other Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 -59 Days Past Due	635	638
60 - 89 Days Past Due	322	419
Greater Than 90 Days	1,161	1,045
Total Past Due	2,118	2,102
Current	14,458	16,861
Total loans	16,576	18,963
Consumer Portfolio Segment | Automobiles
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 -59 Days Past Due	2	11
60 - 89 Days Past Due	3	5
Greater Than 90 Days	2	3
Total Past Due	7	19
Current	784	753
Total loans	791	772
Consumer Portfolio Segment | Consumer Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 -59 Days Past Due	148	157
60 - 89 Days Past Due		7
Greater Than 90 Days	163	168
Total Past Due	311	332
Current	12,734	13,731
Total loans	13,045	14,063
Residential Real Estate | Residential 1-4 family
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 -59 Days Past Due	156	259
60 - 89 Days Past Due	162	406
Greater Than 90 Days	278	970
Total Past Due	596	1,635
Current	8,788	8,129
Total loans	$ 9,384	$ 9,764