Consolidated Statements of Stockholders' Equity (Deficit) - 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, 2012	$ 49,778	$ 38	$ 143,703	$ (47)	$ (93,919)	$ 3
Beginning Balance, shares at Dec. 31, 2012		37,497,703				2,709,300
Stock-based compensation	3,327		3,327
Stock option exercise	$ 357		357
Stock option exercise, shares	115,667	115,667
Restricted stock awards, shares		80,498
Warrant derivative liability reclassified to equity	$ 11		11
Warrant exercises	50		50
Warrant exercises, shares		10,000
Shares issued to Arcion in acquisition of research and development license	2,073	$ 1	2,072
Shares issued to Arcion in acquisition of research and development license, shares		500,516
Warrants issued in connection with notes payable	986		986
Net loss	(57,394)				(57,394)
Ending Balance at Dec. 31, 2013	(812)	$ 39	150,506	(47)	(151,313)	$ 3
Ending 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, shares		1,304,410
Short swing profit return	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-based compensation, shares	0	0	0	0	0	0
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	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