Condensed Consolidated Statement of Changes in Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Preferred Shares	Common Shares	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2017	$ (65,100)	$ 24,364	$ 208,768	$ (4,229)	$ 977,866	$ (1,271,869)
Balance (in shares) at Dec. 31, 2017		328,184,640	272,719,044	(1,697,033)
Balance (Cumulative-effect adjustment) | Accounting Standards Update 2014-09	(218)					(218)
Balance at Jan. 01, 2018	(65,318)	$ 24,364	$ 208,768	$ (4,229)	977,866	(1,272,087)
Balance (in shares) at Jan. 01, 2018		328,184,640	272,719,044	(1,697,033)
Balance at Dec. 31, 2017	(65,100)	$ 24,364	$ 208,768	$ (4,229)	977,866	(1,271,869)
Balance (in shares) at Dec. 31, 2017		328,184,640	272,719,044	(1,697,033)
Issuance of common stock, net of transaction costs	70,007		$ 14,635		55,372
Issuance of common stock, net of transaction costs (shares)			20,616,438
Exercise of stock options	1,548		$ 541		1,007
Exercise of stock options (in shares)			782,553
Vesting of restricted stock units	(2,553)		$ 1,302	$ (2,553)	(1,302)
Vesting of restricted stock units (in shares)			1,838,380	(675,242)
Stock-based compensation	3,754				3,754
Loss for the period	(24,095)					(24,095)
Balance at Mar. 31, 2018	(16,657)	$ 24,364	$ 225,246	$ (6,782)	1,036,697	(1,296,182)
Balance (in shares) at Mar. 31, 2018		328,184,640	295,956,415	(2,372,275)
Balance at Dec. 31, 2017	$ (65,100)	$ 24,364	$ 208,768	$ (4,229)	977,866	(1,271,869)
Balance (in shares) at Dec. 31, 2017		328,184,640	272,719,044	(1,697,033)
Exercise of stock options (in shares)	5,439,239
Loss for the period	$ (82,776)
Balance at Sep. 30, 2018	(52,826)	$ 21,850	$ 232,646	$ (9,867)	1,057,408	(1,354,863)
Balance (in shares) at Sep. 30, 2018		289,317,460	307,309,316	(3,219,598)
Balance at Dec. 31, 2017	(65,100)	$ 24,364	$ 208,768	$ (4,229)	977,866	(1,271,869)
Balance (in shares) at Dec. 31, 2017		328,184,640	272,719,044	(1,697,033)
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)
Balance at Mar. 31, 2018	(16,657)	$ 24,364	$ 225,246	$ (6,782)	1,036,697	(1,296,182)
Balance (in shares) at Mar. 31, 2018		328,184,640	295,956,415	(2,372,275)
Issuance of common stock under employee stock purchase plan	423		$ 85		338
Issuance of common stock under employee stock purchase plan (in shares)			127,872
Exercise of stock options	278		$ 116		162
Exercise of stock options (in shares)			173,679
Vesting of restricted stock units	(127)		$ 60	$ (127)	(60)
Vesting of restricted stock units (in shares)			90,937	(41,252)
Stock-based compensation	3,606				3,606
Loss for the period	(34,210)					(34,210)
Balance at Jun. 30, 2018	(46,687)	$ 24,364	$ 225,507	$ (6,909)	1,040,743	(1,330,392)
Balance (in shares) at Jun. 30, 2018		328,184,640	296,348,903	(2,413,527)
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	14,668		$ 2,932		11,736
Exercise of stock options (in shares)			4,483,007
Vesting of restricted stock units	(2,958)		$ 1,693	$ (2,958)	(1,693)
Vesting of restricted stock units (in shares)			2,590,688	(806,071)
Stock-based compensation	6,661				6,661
Loss for the period	(24,471)					(24,471)
Balance at Sep. 30, 2018	(52,826)	$ 21,850	$ 232,646	$ (9,867)	1,057,408	(1,354,863)
Balance (in shares) at Sep. 30, 2018		289,317,460	307,309,316	(3,219,598)
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)
Exercise of stock options	15,456		$ 2,496		12,960
Exercise of stock options (in shares)			3,838,739
Vesting of restricted stock units	(9,080)		$ 929	$ (9,080)	(929)
Vesting of restricted stock units (in shares)			1,416,124	(526,708)
Stock-based compensation	6,596				6,596
Loss for the period	(24,431)					(24,431)
Balance at Mar. 31, 2019	140,871	$ 21,850	$ 250,088	$ (19,493)	1,301,389	(1,412,963)
Balance (in shares) at Mar. 31, 2019		289,317,460	334,365,726	(3,787,558)
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)
Exercise of stock options (in shares)	5,122,107
Loss for the period	$ (29,713)
Balance at Sep. 30, 2019	595,896	$ 21,850	$ 266,878	$ (20,533)	1,745,946	(1,418,245)
Balance (in shares) at Sep. 30, 2019		289,317,460	361,368,945	(3,841,615)
Balance at Mar. 31, 2019	140,871	$ 21,850	$ 250,088	$ (19,493)	1,301,389	(1,412,963)
Balance (in shares) at Mar. 31, 2019		289,317,460	334,365,726	(3,787,558)
Issuance of common stock under employee stock purchase plan	837		$ 30		807
Issuance of common stock under employee stock purchase plan (in shares)			47,358
Exercise of stock options	1,888		$ 396		1,492
Exercise of stock options (in shares)			619,404
Vesting of restricted stock units	(1,040)		$ 74	$ (1,040)	(74)
Vesting of restricted stock units (in shares)			116,937	(54,057)
Stock-based compensation	8,351				8,351
Loss for the period	(1,820)					(1,820)
Balance at Jun. 30, 2019	149,087	$ 21,850	$ 250,588	$ (20,533)	1,311,965	(1,414,783)
Balance (in shares) at Jun. 30, 2019		289,317,460	335,149,425	(3,841,615)
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
Exercise of stock options	2,200		$ 411		1,789
Exercise of stock options (in shares)			663,964
Stock-based compensation	7,963				7,963
Loss for the period	(3,462)					(3,462)
Balance at Sep. 30, 2019	$ 595,896	$ 21,850	$ 266,878	$ (20,533)	$ 1,745,946	$ (1,418,245)
Balance (in shares) at Sep. 30, 2019		289,317,460	361,368,945	(3,841,615)