CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Treasury Stock	Other Comprehensive Income (Loss)
Balance beginning (in shares) at Dec. 31, 2019		32,399,352
Balance beginning at Dec. 31, 2019	$ (186,017)	$ 324	$ 1,260,551	$ (1,431,801)	$ (2,583)	$ (12,508)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Non-cash stock-based compensation	3,965		3,965
Stock issued under incentive programs (shares)		33,239
Stock issued under incentive programs	5		60		(55)
Issuance of common stock, net of issuance costs (in shares)		21,473,731
Issuance of common stock, net of issuance costs	185,918	$ 215	185,703
Unrealized loss on marketable securities	(132)					(132)
Foreign currency translation adjustment	(1,846)					(1,846)
Net loss	(25,864)			(25,864)
Balance ending (in shares) at Mar. 31, 2020		53,906,322
Balance ending at Mar. 31, 2020	(23,971)	$ 539	1,450,279	(1,457,665)	(2,638)	(14,486)
Balance beginning (in shares) at Dec. 31, 2020		71,350,365
Balance beginning at Dec. 31, 2020	627,209	$ 714	2,535,476	(1,874,199)	(41,806)	7,024
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Non-cash stock-based compensation	53,060		53,060
Stock issued under incentive programs (shares)		541,251
Stock issued under incentive programs	24,099	$ 5	26,745		(2,651)
Issuance of common stock, net of issuance costs (in shares)		2,578,967
Issuance of common stock, net of issuance costs	564,859	$ 26	564,833
Unrealized loss on marketable securities	(9)					(9)
Foreign currency translation adjustment	(7,372)					(7,372)
Net loss	(222,719)			(222,719)
Balance ending (in shares) at Mar. 31, 2021		74,470,583
Balance ending at Mar. 31, 2021	$ 1,039,127	$ 745	$ 3,180,114	$ (2,096,918)	$ (44,457)	$ (357)