Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Observable Inputs (Level 2) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Change in fair value included in earnings	$ (106,536)	$ (124,000)	$ 3,062,575
Fair Value, Measurements, Recurring | Warrants | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance	354,000	615,000	8,682,441
Change in fair value included in earnings	106,536	124,000	(3,062,575)
Exercise of warrants	(427,274)	(385,000)	(5,004,866)
Balance	$ 33,262	$ 354,000	$ 615,000