Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Total
Balance (in shares) at Dec. 31, 2017	73,181,750		41,309
Balance at Dec. 31, 2017	$ 73	$ 422,017	$ (234)	$ (354,863)	$ 66,993
Issuance of restricted stock (in shares)	87,500
Forfeiture of restricted stock (in shares)	(123,911)
Issuance of common stock in At-the-Market offering (net of offering costs) (in shares)	3,989,344
Issuance of common stock in At-the-Market offering (net of offering costs)	$ 4	52,426			52,430
Compensation in respect of restricted stock and options granted to employees, directors and consultants		7,337			7,337
Net loss				(41,529)	(41,529)
Balance (in shares) at Mar. 31, 2018	77,134,683		41,309
Balance at Mar. 31, 2018	$ 77	481,781	$ (234)	(396,392)	85,232
Balance (in shares) at Dec. 31, 2018	83,911,855		41,309
Balance at Dec. 31, 2018	$ 84	552,531	$ (234)	(528,345)	24,036
Issuance of restricted stock (in shares)	23,000
Warrants issued with debt financing		993			993
Forfeiture of restricted stock	$ (67,628)
Issuance of common stock in At-the-Market offering (net of offering costs) (in shares)	4,715,000
Issuance of common stock in At-the-Market offering (net of offering costs)	$ 5	27,494			27,499
Compensation in respect of restricted stock and options granted to employees, directors and consultants		1,882			1,882
Net loss				(35,156)	(35,156)
Balance (in shares) at Mar. 31, 2019	88,582,227		41,309
Balance at Mar. 31, 2019	$ 89	$ 582,900	$ (234)	$ (563,501)	$ 19,254