WARRANTS

9 Months Ended

Sep. 30, 2014

Derivative Instruments and Hedging Activities Disclosure [Abstract]

WARRANTS

7. WARRANTS

The Company has periodically issued warrants in connection with certain common stock offerings. The warrants issued in January and August 2009 were classified as liabilities as opposed to equity due to their settlement terms which required settlement in registered shares. The outstanding warrants classified as liabilities were recorded on the unaudited condensed consolidated balance sheets and adjusted to fair value at each financial reporting period, with changes in the fair value being recorded as “Gain (loss) on change in warrant valuation” in the unaudited condensed consolidated statements of operations and comprehensive loss. Fair value was determined using the Black-Scholes-Merton option-pricing model, which requires the use of significant judgment and estimates for the inputs used in the model. As of September 30, 2014, there were no outstanding warrants as all warrants issued in January and August 2009 have been exercised or expired.

The following table summarizes the reconciliation of the change in value of the Company’s liability classified warrants for each of the periods indicated:

	For the Three Months Ended September 30,						For the Nine Months Ended September 30,
	2014			2013			2014			2013
	(in thousands)
Balance at beginning of the period	$	9,826		$	79,116		$	9,006		$	65,193
(Decrease) increase in value of warrants		(4,256	)		17,160			2,779			46,011
Reclassification to stockholders’ equity upon exercise of warrants		(5,570	)		(60,282	)		(11,785	)		(75,210	)
Balance at end of the period	$	—		$	35,994		$	—		$	35,994

The following table summarizes the Company’s warrant activity for each of the periods indicated:

	For the Three Months Ended September 30,										For the Nine Months Ended September 30,
	2014					2013					2014					2013
	Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price		Shares			Weighted Average Exercise Price
Warrants outstanding at beginning of the period		501,494		$	10.20		2,628,923		$	8.41		791,508		$	10.05		3,127,618		$	8.48
Exercised		(475,901	)		10.32		(1,669,640	)		7.62		(765,915	)		10.12		(2,168,335	)		7.91
Expired		(25,593	)		7.92		—			—		(25,593	)		7.92		—			—
Warrants outstanding at end of the period		—		$	—		959,283		$	9.78		—		$	—		959,283		$	9.78
Warrants exercisable at end of the period		—		$	—		959,283		$	9.78		—		$	—		959,283		$	9.78