Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Shares [Member]	Treasury Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2019	$ 939,425	$ 1,847	$ (63)	$ 1,162,345	$ (224,711)	$ 7
Beginning balance (in shares) at Dec. 31, 2019		60,783,799	250,226
Vesting of restricted shares (in shares)		5,000
Exercise of vested options, value	1,388	$ 3		1,385
Exercise of vested options (in shares)		83,406
Stock-based compensation expense	14,151			14,151
Issuance of common shares related to license agreement	889			889
Issuance of common shares related to license agreement (in shares)		17,830	(17,830)
Other comprehensive loss	(25)					(25)
Net loss	(69,731)				(69,731)
Ending balance at Mar. 31, 2020	886,097	$ 1,850	$ (63)	1,178,770	(294,442)	(18)
Ending balance (in shares) at Mar. 31, 2020		60,890,035	232,396
Beginning balance at Dec. 31, 2019	939,425	$ 1,847	$ (63)	1,162,345	(224,711)	7
Beginning balance (in shares) at Dec. 31, 2019		60,783,799	250,226
Ending balance at Dec. 31, 2020	1,664,234	$ 2,277	$ (63)	2,235,679	(573,576)	(83)
Ending balance (in shares) at Dec. 31, 2020		73,914,844	195,316
Issuance of common shares, net of issuance costs	222,175	$ 45		222,130
Issuance of common shares, net of issuance costs (in shares)		1,353,121
Vesting of restricted shares	3	$ 3
Vesting of restricted shares (in shares)		109,355
Exercise of vested options, value	$ 9,784	$ 15		9,769
Exercise of vested options (in shares)	342,471	342,051
Purchase of common stock under ESPP	$ 751			751
Purchase of common stock under ESPP (in shares)		11,257
Stock-based compensation expense	22,092			22,092
Other comprehensive loss	(378)					(378)
Net loss	(113,163)				(113,163)
Ending balance at Mar. 31, 2021	$ 1,805,498	$ 2,340	$ (63)	$ 2,490,421	$ (686,739)	$ (461)
Ending balance (in shares) at Mar. 31, 2021		75,730,628	195,316