Credit Quality Assessment - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Specific allowance	$ 5,149,000	$ 7,791,000
Non-accrual loans and leases	47,548,000	71,680,000
Restructured accruing	3,614,000	5,286,000
Restructured non-accruing	1,304,000	4,976,000
Restructured Accuring Loan	4,900,000	10,300,000
Restructured Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Specific allowance	1,200,000	1,900,000
Other real estate owned	5,900,000	4,400,000
Restructured accruing	10,100,000	6,900,000
Restructured non-accruing	9,900,000	20,200,000
Financing Receivable Troubled Debt Restructurings Restructured Total	20,000,000	27,100,000
Additional Financing Receivable Troubled Debt Restructurings Restructured	$ 5,100,000	$ 2,600,000