Investment Securities - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 Investment	Sep. 30, 2012	Sep. 30, 2013 Investment	Sep. 30, 2012	Dec. 31, 2012
Investments Debt And Equity Securities [Abstract]
Sustained decline in market value considered Impairment, period			12 months
Investment securities in continuous unrealized loss position, positions temporarily impaired	79		79
Proceeds from sales of securities available-for-sale	$ 17,940	$ 15,118	$ 34,726	$ 10,005,882
Available-for-sale securities, gross realized gains	674	1,671	2,942	344,265
Available-for-sale securities, gross realized losses	0	0	18	315
Assets pledged to secure United States Government and other public funds and for other purposes	$ 62,462,000		$ 62,462,000		$ 65,418,000