Carrying Amount of Loans with Deterioration of Credit Quality (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Loans Acquired with Deteriorated Credit Quality	$ 11,174	$ 16,121
Carrying amount, Net of Allowance	11,086	16,044
Commercial and Industrial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Acquired with Deteriorated Credit Quality	1,840	2,596
Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Acquired with Deteriorated Credit Quality	9,037	13,209
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Acquired with Deteriorated Credit Quality	148	164
Residential Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Acquired with Deteriorated Credit Quality	149	152
Home Equity Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans Acquired with Deteriorated Credit Quality	$ 0	$ 0