Movements of Options Issued and Outstanding (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013		Dec. 31, 2012
Number of Underlying Shares
Numberof underlying shares, Outstanding at begning of the period	715,000
Granted	0
Exercised	0
Expired	0
Forfeited	0
Numberof underlying shares, Outstanding at end of the period	715,000		715,000
Exercisable at December 31,2012	430,000
Weighted Average Exercise Price Per Share
Weighted- Average ExercisePrice PerShare, Outstanding at begining of the period	$ 5.25
Weighted- Average ExercisePrice PerShare, Outstanding at end of the period	$ 5.25		$ 5.25
Exercisable at December 31,2012	$ 5.71
Aggregate Intrinsic Value
Aggregate Intrinsic Value(1), Outstanding at begning of the period	$ 65,700	[1]
Aggregate Intrinsic Value(1), Outstanding at end of the period	375,900	[1]	65,700	[1]
Exercisable at December 31,2012	$ 208,500	[1]
Weighted Average Contractual Life Remaining in Years
Weighted- Average Contractual Life Remaining in Years Outstanding	8 years 2 months 19 days		8 years 5 months 19 days
Weighted-Average ContractualLife Remainingin Years, Exercisable at December 31, 2012	7 years 11 months 23 days

[1] The intrinsic value of the stock options at December 31, 2012, 2011 and 2010 is the amount by which the market value of the Company's common stock of $4.39, $4.76 and $11.24 as of December 31, 2012, 2011 and 2010 exceeds the exercise price of the option.