Loan Portfolio Segment Balances (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 2,565,069	$ 2,531,128
Commercial Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	344,489	346,708
Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	1,974	3,421
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	353,341	356,990
Residential Real Estate Portfolio Segment | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	538,346	523,364
Residential Real Estate Portfolio Segment | Residential Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	122,698	120,314
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	565,820	571,510
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	487,802	456,888
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 150,599	$ 151,933