CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($)	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Treasury Stock	Other Comprehensive Income (Loss)	Total
Balance beginning at Dec. 31, 2018	$ 192,000	$ 1,144,621,000	$ (1,299,107,000)	$ (2,450,000)	$ (11,191,000)	$ (167,935,000)
Balance beginning (in shares) at Dec. 31, 2018	19,245,302
Non-cash stock-based compensation		12,803,000				12,803,000
Stock issued under incentive programs	$ 2,000	1,122,000		(132,000)		992,000
Stock issued under incentive programs (shares)	173,873
Fractional shares purchased in stock split				(1,000)		(1,000)
Issuance of common stock, net of issuance costs	$ 62,000	67,768,000				67,830,000
Issuance of common stock, net of issuance costs, (in shares)	6,156,403
Unrealized (loss) gain on marketable securities					5,000	5,000
Foreign currency translation adjustment					(2,668,000)	(2,668,000)
Net loss			(100,864,000)			(100,864,000)
Balance ending at Sep. 30, 2019	$ 256,000	1,226,314,000	(1,399,971,000)	(2,583,000)	(13,854,000)	(189,838,000)
Balance ending (in shares) at Sep. 30, 2019	25,575,578
Balance beginning at Jun. 30, 2019	$ 235,000	1,210,941,000	(1,381,928,000)	(2,451,000)	(12,290,000)	(185,493,000)
Balance beginning (in shares) at Jun. 30, 2019	23,495,466
Non-cash stock-based compensation		2,624,000				2,624,000
Stock issued under incentive programs	$ 1,000	181,000		(132,000)		50,000
Stock issued under incentive programs (shares)	122,485
Issuance of common stock, net of issuance costs	$ 20,000	12,568,000				12,588,000
Issuance of common stock, net of issuance costs, (in shares)	1,957,627
Foreign currency translation adjustment					(1,564,000)	(1,564,000)
Net loss			(18,043,000)			(18,043,000)
Balance ending at Sep. 30, 2019	$ 256,000	1,226,314,000	(1,399,971,000)	(2,583,000)	(13,854,000)	(189,838,000)
Balance ending (in shares) at Sep. 30, 2019	25,575,578
Balance beginning at Dec. 31, 2019	$ 324,000	1,260,551,000	(1,431,801,000)	(2,583,000)	(12,508,000)	(186,017,000)
Balance beginning (in shares) at Dec. 31, 2019	32,399,352
Balance ending at Jun. 30, 2020	$ 612,000	1,699,072,000	(1,499,325,000)	(2,638,000)	(13,195,000)	184,526,000
Balance ending (in shares) at Jun. 30, 2020	61,262,632
Balance beginning at Dec. 31, 2019	$ 324,000	1,260,551,000	(1,431,801,000)	(2,583,000)	(12,508,000)	(186,017,000)
Balance beginning (in shares) at Dec. 31, 2019	32,399,352
Preferred stock beneficial conversion feature	$ 0	24,139,000	(24,139,000)	0	0	0
Non-cash stock-based compensation		77,602,000				77,602,000
Stock issued under incentive programs	$ 19,000	35,689,000		(38,624,000)		(2,916,000)
Stock issued under incentive programs (shares)	1,884,399
Issuance of common stock, net of issuance costs	$ 290,000	450,663,000				450,953,000
Issuance of common stock, net of issuance costs, (in shares)	29,035,137
Unrealized (loss) gain on marketable securities					18,000	18,000
Foreign currency translation adjustment					7,495,000	7,495,000
Net loss			(240,695,000)			(240,695,000)
Balance ending at Sep. 30, 2020	$ 633,000	1,848,644,000	(1,696,635,000)	(41,207,000)	(4,995,000)	106,440,000
Balance ending (in shares) at Sep. 30, 2020	63,318,888
Balance beginning at Jun. 30, 2020	$ 612,000	1,699,072,000	(1,499,325,000)	(2,638,000)	(13,195,000)	184,526,000
Balance beginning (in shares) at Jun. 30, 2020	61,262,632
Non-cash stock-based compensation		65,705,000				65,705,000
Stock issued under incentive programs	$ 16,000	26,682,000		(38,569,000)		(11,871,000)
Stock issued under incentive programs (shares)	1,534,345
Issuance of common stock, net of issuance costs	$ 5,000	57,185,000				57,190,000
Issuance of common stock, net of issuance costs, (in shares)	521,911
Unrealized (loss) gain on marketable securities					(26,000)	(26,000)
Foreign currency translation adjustment					8,226,000	8,226,000
Net loss			(197,310,000)			(197,310,000)
Balance ending at Sep. 30, 2020	$ 633,000	$ 1,848,644,000	$ (1,696,635,000)	$ (41,207,000)	$ (4,995,000)	$ 106,440,000
Balance ending (in shares) at Sep. 30, 2020	63,318,888