Information by Class Regarding Troubled Debt Restructurings which had Payments Default (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012 Loan	Dec. 31, 2011 Loan
Financing Receivable, Modifications [Line Items]
Number of Loans	7	2
Pre-Modification Outstanding Recorded Balance	$ 2,528	$ 619
Post-Modification Outstanding Recorded Balance	2,384	464
Commercial & Industrial Loans
Financing Receivable, Modifications [Line Items]
Number of Loans	5
Pre-Modification Outstanding Recorded Balance	274
Post-Modification Outstanding Recorded Balance	274
Construction & Development
Financing Receivable, Modifications [Line Items]
Number of Loans	1	1
Pre-Modification Outstanding Recorded Balance	553	573
Post-Modification Outstanding Recorded Balance	409	418
Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans	1	1
Pre-Modification Outstanding Recorded Balance	1,701	46
Post-Modification Outstanding Recorded Balance	$ 1,701	$ 46