Consolidated Statements of Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Series A Preferred Stock [Member]
Beginning Balance at Dec. 31, 2013	$ (812)	$ 39	$ 150,506	$ (47)	$ (151,313)	$ 3
Beginning Balance, shares at Dec. 31, 2013		38,204,384				2,709,300
Stock-based compensation	6,883		6,883
Stock option exercise	$ 4,580	$ 1	4,579
Stock option exercise, shares	1,332,563	1,332,563
Restricted stock awards, shares		473,893
Warrant derivative liability reclassified to equity	$ 17,478		17,478
Warrant exercises	7,741	$ 2	7,739
Warrant exercises, shares		1,999,153
Cashless exercise of warrants	0	$ 0	0	0	0	$ 0
Cashless exercise of warrants, shares		218,367
Shares issued pursuant to registered direct offering, net	58,182	$ 8	58,174
Shares issued pursuant to registered direct offering, net shares		7,500,000
Shares issued pursuant to an at the market offering, net	14,480	$ 1	14,479
Shares issued pursuant to an at the market offering, net, shares		1,304,410
Short swing profit return / Issuance of warrants	82		82
Conversion of preferred shares to common shares		$ 1				$ (1)
Conversion of preferred shares to common shares, shares		570,300				(570,300)
Net loss	(54,218)				(54,218)
Ending Balance at Dec. 31, 2014	54,396	$ 52	259,920	(47)	(205,531)	$ 2
Ending Balance, shares at Dec. 31, 2014		51,603,070				2,139,000
Stock-based compensation	14,249		14,249
Stock option exercise	$ 755		755
Stock option exercise, shares	235,480	223,923
Restricted stock awards	$ 1	$ 1
Restricted stock awards, shares		857,677
Warrant exercises	1		1
Warrant exercises, shares		284
Short swing profit return / Issuance of warrants	6		6
Conversion of preferred shares to common shares, shares		45,845				(45,845)
Equity financing costs	(40)		(40)
Net loss	(37,672)				(37,672)
Ending Balance at Dec. 31, 2015	31,696	$ 53	274,891	(47)	(243,203)	$ 2
Ending Balance, shares at Dec. 31, 2015		52,730,799				2,093,155
Stock-based compensation	14,931		14,931
Stock option exercise	$ 297		297
Stock option exercise, shares	147,425	147,426
Restricted stock awards, shares		592,065
Common stock issuance upon retirement	$ 2,460	$ 1	2,459
Common stock issuance upon retirement, shares		663,221
Short swing profit return / Issuance of warrants	49		49
Equity financing costs	40		40
Net loss	(67,138)				(67,138)
Ending Balance at Dec. 31, 2016	$ (17,665)	$ 54	$ 292,667	$ (47)	$ (310,341)	$ 2
Ending Balance, shares at Dec. 31, 2016		54,133,511				2,093,155