Stock Warrants (Tables)

12 Months Ended

Dec. 31, 2012

Stock Warrants

Schedule of common and convertible preferred stock warrant activity of the Company

(in thousands, except per share amounts)	Warrants for the purchase of common stock			Weighted average exercise price		Warrants for the purchase of convertible preferred stock			Weighted average exercise price
Balance—December 31, 2009		2,937			2.35		317		$	3.42
Exercised		—					(11	)	$	1.89
Balance—December 31, 2010		2,937			2.93		306		$	3.48
Expired		(1	)		2.47		—			—
Exercised		(296	)		2.46		(4	)	$	1.89
Balance—December 31, 2011		2,640		$	2.98		302		$	3.50
Conversion		302		$	3.50		(302	)	$	3.50
Expired		—			—		—			—
Exercised		(100	)	$	2.63		—			—
Balance—December 31, 2012		2,842		$	3.05		—			—