Non-Accrual Loan, Segregated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 23,410	$ 30,711
Commercial | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	2,450	7,592
Commercial | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	5,989	9,314
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,315	1,160
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	10,791	10,080
Consumer loans | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	1,656	2,081
Consumer loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	96	89
Consumer loans | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	37	24
Consumer loans | Boat/RV
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 1,076	$ 371