Consolidated Statements of Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Total
Balance at Dec. 31, 2016	$ 57	$ 272,432	$ (234)	$ (236,387)	$ 35,868
Balance (in shares) at Dec. 31, 2016	56,820,422		41,309
Issuance of common stock in connection with exercise of warrants		2,142			2,142
Issuance of common stock in connection with exercise of warrants (in shares)	887,585
Issuance of restricted stock	$ 2	(2)
Issuance of restricted stock (in shares)	1,836,511
Forfeiture of restricted stock (in shares)	(53,875)
Issuance of common stock (net of offering costs)	$ 6	53,634			53,640
Issuance of common stock (net of offering costs) (in shares)	5,897,436
Issuance of common stock in At-the-Market offerings (net of offering costs)	$ 8	77,865			77,873
Compensation in respect of restricted stock granted to employees, directors and consultants		15,945			15,945
Net loss				(118,476)	(118,476)
Balance at Dec. 31, 2017	$ 73	422,017	$ (234)	(354,863)	66,993
Balance (in shares) at Dec. 31, 2017	73,181,750		41,309
Issuance of common stock in At-the-Market offerings (in shares)	7,793,671
Issuance of restricted stock	$ 2	(2)
Issuance of restricted stock (in shares)	1,562,211
Forfeiture of restricted stock (in shares)	(191,196)
Issuance of common stock (net of offering costs)	$ 9	113,630			113,639
Compensation in respect of restricted stock granted to employees, directors and consultants		12,886			12,886
Shares issued in connection with in-licensing agreements		4,000			4,000
Shares issued in connection with in-licensing agreements (in shares)	333,868
Net loss				(173,482)	(173,482)
Balance at Dec. 31, 2018	$ 84	552,531	$ (234)	(528,345)	24,036
Balance (in shares) at Dec. 31, 2018	83,911,855		41,309
Issuance of common stock in At-the-Market offerings (in shares)	9,025,222
Issuance of restricted stock	$ 1	(1)
Issuance of restricted stock (in shares)	1,851,520
Warrants issued with debt financing		993			993
Forfeiture of restricted stock (in shares)	(116,463)
Issuance of common stock (net of offering costs)	$ 10	77,465			77,475
Issuance of common stock (net of offering costs) (in shares)	10,149,783
Issuance of common stock in At-the-Market offerings (net of offering costs)	$ 14	97,533			97,547
Compensation in respect of restricted stock granted to employees, directors and consultants		11,335			11,335
Shares issued in connection with in-licensing agreements		100			100
Shares issued in connection with in-licensing agreements (in shares)	8,383
Net loss				(172,871)	(172,871)
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 At-the-Market offerings (in shares)	13,620,165