Condensed Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common shares	Accumulated deficit	Accumulated other comprehensive loss	Additional paid-in capital
Beginning balance (in shares) at Dec. 31, 2018		31,977,668
Beginning balance at Dec. 31, 2018	$ 180,490	$ 320,074	$ (145,272)	$ (6,659)	$ 12,347
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares on exercise of options (in shares)		52,130
Issuance of common shares on exercise of stock options	419	$ 549			(130)
Issuance of common shares through employee share purchase plan (in shares)		18,681
Issuance of common shares through employee stock purchase plan	325	$ 325
Fair value adjustments upon reclassification of options to liabilities	(119)				(119)
Stock-based compensation	2,533				2,533
Net loss	(13,641)		(13,641)
Ending balance (in shares) at Mar. 31, 2019		32,048,479
Ending balance at Mar. 31, 2019	170,007	$ 320,948	(158,913)	(6,659)	14,631
Beginning balance (in shares) at Dec. 31, 2018		31,977,668
Beginning balance at Dec. 31, 2018	180,490	$ 320,074	(145,272)	(6,659)	12,347
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(42,718)
Ending balance (in shares) at Jun. 30, 2019		39,177,669
Ending balance at Jun. 30, 2019	334,017	$ 441,174	(187,990)	(6,659)	87,492
Beginning balance (in shares) at Mar. 31, 2019		32,048,479
Beginning balance at Mar. 31, 2019	170,007	$ 320,948	(158,913)	(6,659)	14,631
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares on exercise of options (in shares)		115,298
Issuance of common shares on exercise of stock options	2,044	$ 2,285			(241)
Stock-based compensation	3,038				3,038
Issuance of common shares and warrants in connection with public offering (in shares)		7,013,892
Issuance of common shares and pre-funded warrants in connection with public offering (Note 8)	188,005	$ 117,941			70,064
Net loss	(29,077)		(29,077)
Ending balance (in shares) at Jun. 30, 2019		39,177,669
Ending balance at Jun. 30, 2019	$ 334,017	$ 441,174	(187,990)	(6,659)	87,492
Beginning balance (in shares) at Dec. 31, 2019	39,564,529	39,564,529
Beginning balance at Dec. 31, 2019	$ 245,681	$ 450,210	(290,709)	(6,659)	92,839
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares on exercise of options (in shares)		122,492
Issuance of common shares on exercise of stock options	2,013	$ 2,767			(754)
Issuance of common shares through employee share purchase plan (in shares)		21,451
Issuance of common shares through employee stock purchase plan	615	$ 615
Fair value adjustments upon reclassification of options to liabilities	(110)				(110)
Stock-based compensation	4,446				4,446
Issuance of common shares and warrants in connection with public offering (in shares)		5,824,729
Issuance of common shares and pre-funded warrants in connection with public offering (Note 8)	300,910	$ 254,018			46,892
Net loss	(31,136)		(31,136)
Ending balance (in shares) at Mar. 31, 2020		45,533,201
Ending balance at Mar. 31, 2020	$ 522,419	$ 707,610	(321,845)	(6,659)	143,313
Beginning balance (in shares) at Dec. 31, 2019	39,564,529	39,564,529
Beginning balance at Dec. 31, 2019	$ 245,681	$ 450,210	(290,709)	(6,659)	92,839
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (70,097)
Ending balance (in shares) at Jun. 30, 2020	45,563,155	45,563,155
Ending balance at Jun. 30, 2020	$ 491,253	$ 708,319	(360,806)	(6,659)	150,399
Beginning balance (in shares) at Mar. 31, 2020		45,533,201
Beginning balance at Mar. 31, 2020	522,419	$ 707,610	(321,845)	(6,659)	143,313
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares on exercise of options (in shares)		29,954
Issuance of common shares on exercise of stock options	557	$ 709			(152)
Stock-based compensation	7,238				7,238
Net loss	$ (38,961)		(38,961)
Ending balance (in shares) at Jun. 30, 2020	45,563,155	45,563,155
Ending balance at Jun. 30, 2020	$ 491,253	$ 708,319	$ (360,806)	$ (6,659)	$ 150,399