Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012 Loan	Dec. 31, 2011 Loan
Financing Receivable, Modifications [Line Items]
Number of Loans	9	5
Pre-Modification Outstanding Recorded Balance	$ 3,216	$ 2,770
Post-Modification Outstanding Recorded Balance	3,216	2,770
Commercial & Industrial Loans
Financing Receivable, Modifications [Line Items]
Number of Loans		1
Pre-Modification Outstanding Recorded Balance		430
Post-Modification Outstanding Recorded Balance		430
Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans	3	3
Pre-Modification Outstanding Recorded Balance	2,229	2,198
Post-Modification Outstanding Recorded Balance	2,229	2,198
Residential Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans	5	1
Pre-Modification Outstanding Recorded Balance	968	142
Post-Modification Outstanding Recorded Balance	968	142
Consumer Loan
Financing Receivable, Modifications [Line Items]
Number of Loans	1
Pre-Modification Outstanding Recorded Balance	19
Post-Modification Outstanding Recorded Balance	$ 19