Consolidated Statements of Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Deficit	Series A Preferred Stock	Series B Preferred Stock
Beginning balance, preferred stock (in shares) at Dec. 31, 2016						2,093,155	0
Beginning Balance at Dec. 31, 2016	$ (17,665)	$ 54	$ 292,667	$ (47)	$ (310,341)	$ 2	$ 0
Beginning balance (in shares) at Dec. 31, 2016		54,133,511
Stock-based compensation	14,801		14,801
Stock option exercises	$ 439		439
Stock option exercises (in shares)	202,519	202,519
Restricted stock awards		$ 2	(2)
Restricted stock awards (in shares)		1,568,042
Issuance of warrants	$ 6,017		6,017
Net income (loss)	5,285				5,285
Ending balance, preferred stock (in shares) at Dec. 31, 2017						2,093,155	0
Ending Balance at Dec. 31, 2017	8,877	$ 56	313,922	(47)	(305,056)	$ 2	$ 0
Ending balance (in shares) at Dec. 31, 2017		55,904,072
Stock-based compensation	5,941		5,941
Stock option exercises	$ 670		670
Stock option exercises (in shares)	350,441	350,441
Restricted stock awards		$ 2	(2)
Restricted stock awards (in shares)		1,733,731
Common stock issuance upon retirement		$ 2	(2)
Common stock issuance upon retirement, shares	2,119,925	2,249,925
Series B issuance, net of issuance costs	$ 47,986		47,986
Series B issuance, net of issuance costs (in shares)							5,000
Series B conversion to Common Stock		$ 11	(11)
Series B conversion to Common Stock (in shares)		10,555,556					(1,900)
Series B beneficial conversion feature	(12,500)		12,500		(12,500)
Cumulative effect of accounting change	135				135
Net income (loss)	(33,867)				(33,867)
Ending balance, preferred stock (in shares) at Dec. 31, 2018						2,093,155	3,100
Ending Balance at Dec. 31, 2018	$ 29,742	$ 71	381,004	(47)	(351,288)	$ 2	$ 0
Ending balance (in shares) at Dec. 31, 2018	70,778,234	70,793,725
Stock-based compensation	$ 5,418		5,418
Stock option exercises	$ 2,319		2,319
Stock option exercises (in shares)	799,800	799,800
Restricted stock awards		$ 1	(1)
Restricted stock awards (in shares)		806,661
Common stock issuance upon retirement, shares	2,119,925
Series B conversion to Common Stock		$ 14	(14)
Series B conversion to Common Stock (in shares)		13,788,888					(2,482)
Series B beneficial conversion feature	$ (12,500)
Equity offering, net of finance costs, value	47,590	$ 10	47,580
Equity offering, net of finance costs (in shares)		10,000,000
Net income (loss)	(15,305)				(15,305)
Ending balance, preferred stock (in shares) at Dec. 31, 2019						2,093,155	618
Ending Balance at Dec. 31, 2019	$ 69,764	$ 96	$ 436,306	$ (47)	$ (366,593)	$ 2	$ 0
Ending balance (in shares) at Dec. 31, 2019	96,173,583	96,189,074