Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Observable Inputs (Level 2) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Change in fair value included in earnings	$ 451,000	$ 629,000	$ (23,000)	$ 3,183,252
Fair Value, Measurements, Recurring | Warrants | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance at January 1, 2012			615,000
Change in fair value included in earnings			23,000
Exercise of warrants			(385,000)
Balance at September 30, 2012	$ 253,000		$ 253,000