Loans By Class Modified As Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Mortgage Loan On Real Estate Number Of Loans	2	10
Financing Receivable Modification Pre Modification Recorded Investment	$ 9	$ 11,640
Financing Receivable Modification Post Modification Recorded Investment	9	11,349
Commercial and Industrial Loans and Leases [Member]
Financing Receivable, Modifications [Line Items]
Mortgage Loan On Real Estate Number Of Loans	2	4
Financing Receivable Modification Pre Modification Recorded Investment	9	4,541
Financing Receivable Modification Post Modification Recorded Investment	9	4,499
Commercial Real Estate Loans [Member]
Financing Receivable, Modifications [Line Items]
Mortgage Loan On Real Estate Number Of Loans	0	6
Financing Receivable Modification Pre Modification Recorded Investment	0	7,099
Financing Receivable Modification Post Modification Recorded Investment	$ 0	$ 6,850