Allowance for Loan Losses - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012 SecurityLoan	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012 SecurityLoan	Dec. 31, 2012
Receivables [Abstract]
Historical loss percentage period for portfolio segments			3 years
Adequate allowance for loan losses	$ 17,297		$ 17,297		$ 19,742
Number of days past due for loans to be considered as nonperforming			90 days
Reasonable period for nonperforming TDRs to be returned to performing status			6 months
Number of days reaching where loans are considered for nonaccrual status			90 days
Defaulted loans	0	0	2	0
Loans			$ 66
Impaired loans	Greater than $500		Greater than $500
Due days for testing impairment			60 days