Past Due Loan Trends for Corporation's Loans Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	$ 1,330	$ 2,580
60 - 89 Days Past Due	602	727
Greater Than 90 Days	10,539	11,951
Total Past Due	12,471	14,816
90 days Past Due & Still Accruing		442
Current	122,566	145,395
Total loans	135,037	160,653
Commercial Portfolio Segment | Commercial Non Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	36	485
60 - 89 Days Past Due		139
Greater Than 90 Days	643	996
Total Past Due	679	1,237
90 days Past Due & Still Accruing		383
Current	8,921	11,319
Total loans	9,600	12,939
Commercial Portfolio Segment | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	437	714
60 - 89 Days Past Due	91	472
Greater Than 90 Days	7,522	8,046
Total Past Due	8,050	9,232
Current	71,753	88,315
Total loans	79,803	97,547
Consumer Portfolio Segment | Other Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	90	422
60 - 89 Days Past Due	139	69
Greater Than 90 Days	1,287	2,052
Total Past Due	1,516	2,543
Current	18,507	19,753
Total loans	20,023	22,296
Consumer Portfolio Segment | Automobiles
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	11	69
60 - 89 Days Past Due	8
Greater Than 90 Days	6
Total Past Due	25	69
Current	793	874
Total loans	818	943
Consumer Portfolio Segment | Consumer Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	245	408
60 - 89 Days Past Due	80	47
Greater Than 90 Days	537	182
Total Past Due	862	578
90 days Past Due & Still Accruing		59
Current	13,680	13,953
Total loans	14,542	14,590
Residential Real Estate | Residential 1-4 family
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	511	482
60 - 89 Days Past Due	284
Greater Than 90 Days	544	675
Total Past Due	1,339	1,157
Current	8,912	11,181
Total loans	$ 10,251	$ 12,338