Reconciliation of Provision For Income Taxes Determined at Local Income Tax Rate to Effective Income Tax Rate (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Effective Income Tax Rate [Line Items]
Pre-tax income	$ 75,884,367	$ 78,672,847	$ 70,457,233
United States federal corporate income tax rate	34.00%	34.00%	34.00%
Income tax computed at United States statutory corporate income tax rate	25,800,685	26,748,768	23,955,459
Reconciling items:
Loss not recognized as deferred tax assets	962,173	1,155,378	771,079
Non-deductible expenses	14,492	197,375	175,696
Change in fair value of warrants	39,068	17,241	(1,071,460)
Rate differential for PRC earnings	(7,091,501)	(7,399,559)	(6,260,780)
Other	0	11,641	(246,294)
Income Tax Expense (Benefit)	$ 19,724,917	$ 20,730,844	$ 17,323,700