Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended		12 Months Ended
	Jun. 30, 2014	Sep. 30, 2014	Aug. 31, 2014	Dec. 31, 2013
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Expense related to the settlement of the assessment with the FDIC	$ 10,300,000
Outstanding claims due from the FDIC, net of settlement			21,100,000
Interest that would have been recorded on non - accrual loans		1,000,000
Interest recovered on non - accrual loans		1,000,000
Non-accrual loans		83,154,000		99,657,000
Troubled debt restructuring		18,000,000		25,000,000
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
Troubled Debt Restructurings [Member]
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans		$ 10,000,000