Loans and Allowance For Loan Losses - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2012 Minimum [Member]
Receivables [Abstract]
Bank wide delinquency of loans in percentage	2.89%	3.71%
Bank wide delinquency of loans, 30 to 59 days delinquent, percentage	0.61%	0.43%
Bank wide delinquency of loans, 60 to 89 days delinquent, percentage	0.32%	0.30%
Allocated reserves of nonaccrual TDR loans	$ 392
Loans and leases receivable, impaired, commitment to lend	$ 390
Accounts, Notes, Loans and Financing Receivable [Line Items]
Time period of repayment based on delinquency period one			59 days	30 days
Time period of repayment based on delinquency period two			89 days	60 days
Time period of repayment based on delinquency period three				90 days