Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Interest that would have been recognized on nonaccrual loans	$ 4,900,000
Interest recovered on nonaccrual loans	4,100,000
Non-Accrual Loans	119,708,000	137,615,000
Troubled Debt Restructuring	29,700,000	32,200,000
Minimum Bank Portfolio loan need to be reviewed	1,000,000
Restructured Commercial Loan [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-Accrual Loans	$ 19,100,000