Condensed Consolidated Statements of Changes in Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Total
Balance at Dec. 31, 2019	$ 109	$ 739,956	$ (234)	$ (701,216)	$ 38,615
Balance (in shares) at Dec. 31, 2019	109,425,243		41,309
Issuance of common stock in connection with exercise of options		80			80
Issuance of common stock in connection with exercise of options	19,750
Issuance of restricted stock	$ 1	(1)
Issuance of restricted stock (in shares)	774,300
Forfeiture of restricted stock (in shares)	(10,000)
Compensation in respect of restricted stock granted to employees, directors and consultants		11,068			11,068
Net loss				(51,116)	(51,116)
Balance at Mar. 31, 2020	$ 110	751,103	$ (234)	(752,332)	(1,353)
Balance (in shares) at Mar. 31, 2020	110,209,293		41,309
Balance at Dec. 31, 2020	$ 141	1,500,040	$ (234)	(980,597)	519,350
Balance (in shares) at Dec. 31, 2020	140,617,606		41,309
Issuance of common stock in connection with exercise of options		128			128
Issuance of common stock in connection with exercise of options	31,245
Issuance of restricted stock	$ 1	(1)
Issuance of restricted stock (in shares)	893,488
Forfeiture of restricted stock (in shares)	(21,643)
Offering costs paid		(183)			(183)
Compensation in respect of restricted stock granted to employees, directors and consultants		16,618			16,618
Net loss				(90,628)	(90,628)
Balance at Mar. 31, 2021	$ 142	$ 1,516,602	$ (234)	$ (1,071,225)	$ 445,285
Balance (in shares) at Mar. 31, 2021	141,520,696		41,309