CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Balance beginning (in shares) at Dec. 31, 2017		16,184,241
Balance beginning at Dec. 31, 2017	$ (101,732)	$ 162	$ 1,023,532	$ (1,114,359)	$ (2,450)	$ (8,617)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued under incentive programs (in shares)		120,561
Stock issued under incentive programs	2,745	$ 1	2,744
Restricted stock cancelled		(938)
Issuance of common stock, net of issuance costs, (in shares)		2,941,438
Issuance of common stock, net of issuance costs	100,060	$ 29	100,031
Unrealized gain (loss) on marketable securities	12					12
Foreign currency translation adjustment	(2,586)					(2,586)
Net loss	(184,748)			(184,748)
Balance ending (in shares) at Dec. 31, 2018		19,245,302
Balance ending at Dec. 31, 2018	(167,935)	$ 192	1,144,621	(1,299,107)	(2,450)	(11,191)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Non-cash stock-based compensation	17,048		17,048
Stock issued under incentive programs (in shares)		173,873
Fractional shares purchased in stock split	(1)				(1)
Exercise of stock options/Purchases under ESPP	992	$ 2	1,122		(132)
Issuance of common stock, net of issuance costs, (in shares)		12,980,177
Issuance of common stock, net of issuance costs	97,890	$ 130	97,760
Unrealized gain (loss) on marketable securities	5					5
Foreign currency translation adjustment	(1,322)					(1,322)
Net loss	(132,694)			(132,694)
Balance ending (in shares) at Dec. 31, 2019		32,399,352
Balance ending 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	128,035		128,035
Stock issued under incentive programs (in shares)		2,168,725
Stock issued under incentive programs	$ 5,246	$ 22	44,447		(39,223)
Restricted stock cancelled	(54,415)
Preferred stock beneficial conversion feature	$ 0		24,139	(24,139)
Conversion of preferred stock (in shares)		4,388,850
Conversion of preferred stock	199,822	$ 44	199,778
Exercise of stock options/Purchases under ESPP			199,800
Issuance of common stock, net of issuance costs, (in shares)		32,393,438
Issuance of common stock, net of issuance costs	878,850	$ 324	878,526
Unrealized gain (loss) on marketable securities	9					9
Foreign currency translation adjustment	19,523					19,523
Net loss	(418,259)			(418,259)
Balance ending (in shares) at Dec. 31, 2020		71,350,365
Balance ending at Dec. 31, 2020	$ 627,209	$ 714	$ 2,535,476	$ (1,874,199)	$ (41,806)	$ 7,024