Reconciliation of Basic and Diluted Net Income Per Share (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income	$ 8,764,990	$ 5,233,998	$ 15,919,631	$ 39,241,609
Weighted average number of common shares outstanding - Basic	65,963,502	65,953,462	65,963,502	65,905,667
Effect of dilutive securities:
Unexercised warrants and options	0	184,106	0	379,703
Weighted average number of common shares outstanding - Diluted	65,963,502	66,137,568	65,963,502	66,285,370
Earnings per share-Basic	$ 0.13	$ 0.08	$ 0.24	$ 0.60
Earnings per share-Diluted	$ 0.13	$ 0.08	$ 0.24	$ 0.59