Derivative Instruments (Tables)

9 Months Ended

Sep. 30, 2012

Derivative Instruments [Abstract]

Fair value of warrants

	September 30, 2012
Risk-free interest rate	0.30%-0.34%
Expected dividend yield	0%
Expected term	2.92-3.18 years
Expected volatility	60.3%

Changes in derivative warrant liability

	Nine Months Ended September 30,
	2012			2011
Balance at December 31,	$	35,473,230		$	10,647,190
Decrease in the fair value of the warrants		(21,436,653	)		(6,559,835	)
Reduction in derivative liability due to exercise of warrants		(3,235,722	)		—
Balance at September 30,	$	10,800,855		$	4,087,355