Troubled Debt Restructurings that Defaulted Subsequent to Modifications Occurring within Previous Twelve Months, Disaggregated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012 SecurityLoan	Sep. 30, 2011 SecurityLoan	Sep. 30, 2012 SecurityLoan	Sep. 30, 2011 SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans	9	23	13	48
Number of Loans	$ 443	$ 8,505	$ 961	$ 26,431
Real Estate Loan [Member] | Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans				1
Number of Loans				1,425
Real Estate Loan [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans				2
Number of Loans				1,805
Real Estate Loan [Member] | Residential Property [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1		1
Number of Loans		449		449
Commercial and Industrial Loans [Member] | Unsecured [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	3	8	6	18
Number of Loans	171	3,344	431	6,055
Commercial and Industrial Loans [Member] | Secured by Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		3		9
Number of Loans		3,137		10,684
Commercial and Industrial Loans [Member] | Commercial Lines of Credit [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans			1
Number of Loans			258
Commercial and Industrial Loans [Member] | SBA Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	6	11	6	17
Number of Loans	$ 272	$ 1,575	$ 272	$ 6,013