Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013 Times	Jun. 30, 2012	Jun. 30, 2013 Times	Jun. 30, 2012	Dec. 31, 2012 Times
Accounts, Notes, Loans and Financing Receivable [Line Items]
Days principal payments should be past due for recognition of income on a loan be discontinued and previously accrued interest is reversed	90 days		90 days
Loan charge-off, amount	$ 276,000	$ 152,000	$ 594,000	$ 638,000
Loan portfolio risk factor	1.18		1.18		1.15
Increase in estimated allowance for loan losses			74,000
Days loans are past due to be nonperforming loans			90 days		90 days
Installment Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan charge-off period			90 days
Bank Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan charge-off period			45 days
Qualitative Factor Economic Condition
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio risk factor	1.20		1.20		1.20
Qualitative Factor Past Due Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio risk factor	1.20		1.20		1.20
Qualitative Factor Other Internal and External Factors
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio risk factor	1.30		1.30		1.20
Overall Qualitative Factor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in estimated allowance for loan losses			476,000		419,000
Classified Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in estimated allowance for loan losses			590,000		664,000
Partial charge-off loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan charge-off, amount			489,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period of performance borrower need to demonstrate for a loan be restored to accrual status			6 months
Value of significant property	$ 200,000		$ 200,000