Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Shares	Common Shares	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Balance at Dec. 31, 2017	$ (65,100)		$ 24,364	$ 208,768	$ (4,229)	$ 977,866	$ (1,271,869)
Balance (Accounting Standards Update 2014-09) at Dec. 31, 2017		$ (218)						$ (218)
Balance (in shares) at Dec. 31, 2017			328,184,640	272,719,044	(1,697,033)
Accounting Standards Update [Extensible List]							us-gaap:AccountingStandardsUpdate201409Member
Balance at Dec. 31, 2017	(65,318)		$ 24,364	$ 208,768	$ (4,229)	977,866	$ (1,272,087)
Balance (in shares) at Dec. 31, 2017			328,184,640	272,719,044	(1,697,033)
Issuance of common stock, net of transaction costs	264,840			$ 21,744		243,096
Issuance of common stock, net of transaction costs (shares)				31,727,550
Issuance of common stock under employee stock purchase plan	1,043			$ 203		840
Issuance of common stock under employee stock purchase plan (in shares)				312,257
Exchange of exchangeable senior notes, net of transaction costs	29,369			$ 5,011		24,358
Exchange of exchangeable senior notes, net of transaction costs (in shares)				7,716,046
Conversion of Series A Convertible Preferred Stock, net	(39)		$ (2,514)	$ 2,514		(39)
Conversion of Series A Convertible Preferred Stock, net (in shares)			(38,867,180)	3,886,718
Exercise of stock options	26,402			$ 5,309		21,093
Exercise of stock options (in shares)				8,138,305
Vesting of restricted stock units	(6,184)			$ 3,114	$ (6,184)	(3,114)
Vesting of restricted stock units (in shares)				4,610,943	(1,563,817)
Stock-based compensation	18,662					18,662
Loss for the period	(116,445)						(116,445)
Balance at Dec. 31, 2018	152,330		$ 21,850	$ 246,663	$ (10,413)	1,282,762	(1,388,532)
Balance (in shares) at Dec. 31, 2018			289,317,460	329,110,863	(3,260,850)
Issuance of common stock, net of transaction costs	440,108			$ 15,879		424,229
Issuance of common stock, net of transaction costs (shares)				25,555,556
Issuance of common stock under employee stock purchase plan	2,165			$ 79		2,086
Issuance of common stock under employee stock purchase plan (in shares)				123,031
Issuance of common stock for milestone payment	6,216			$ 173		6,043
Issuance of common stock for milestone payment (in shares)				257,713
Exercise of stock options	24,478			$ 3,876		20,602
Exercise of stock options (in shares)				5,997,919
Vesting of restricted stock units	(25,487)			$ 2,503	$ (25,487)	(2,503)
Vesting of restricted stock units (in shares)				3,969,811	(1,650,142)
Stock-based compensation	31,098					31,098
Loss for the period	(22,645)						(22,645)
Balance at Dec. 31, 2019	608,263		$ 21,850	$ 269,173	$ (35,900)	1,764,317	(1,411,177)
Balance (in shares) at Dec. 31, 2019			289,317,460	365,014,893	(4,910,992)
Issuance of common stock under employee stock purchase plan	1,957			$ 225		1,732
Issuance of common stock under employee stock purchase plan (in shares)				347,153
Conversion of Series A Convertible Preferred Stock, net	(504)		$ (21,850)	$ 18,020		3,326
Conversion of Series A Convertible Preferred Stock, net (in shares)			(289,317,460)	28,931,746
Exercise of stock options	$ 5,158			$ 1,062		4,096
Exercise of stock options (in shares)	1,623,000			1,623,460
Vesting of restricted stock units	$ (15,182)			$ 1,635	$ (15,182)	(1,635)
Vesting of restricted stock units (in shares)				2,507,748	(975,927)
Stock-based compensation	45,813					45,813
Loss for the period	(18,000)						(18,000)
Balance at Dec. 31, 2020	$ 627,505			$ 290,115	$ (51,082)	$ 1,817,649	$ (1,429,177)
Balance (in shares) at Dec. 31, 2020				398,425,000	(5,886,919)