Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Interest that would have been recognized on nonaccrual loans	$ 3,700,000
Interest recovered on nonaccrual loans	2,100,000
Non-Accrual Loans	132,733,000	137,615,000
Troubled Debt Restructuring	33,700,000	32,200,000
Minimum Bank Portfolio loan need to be reviewed	1,000,000
Performing [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Period for which payments of principal and interest are past due	Less than 90 days
Restructured Commercial Loan [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-Accrual Loans	$ 20,600,000