Consolidated statements of shareholders' equity - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid In Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Income	Treasury Stock
Balance at Dec. 31, 2019	$ 294,660	$ 4	$ 734,734	$ (444,698)	$ 4,620
Balance, Shares at Dec. 31, 2019		68,237,247
Issuance of ordinary shares upon vesting of restricted shares	0	$ 0	0
Issuance of ordinary shares upon vesting of restricted shares, Shares		80,200
Exercise of shares option	346	$ 0	346
Exercise of shares option, Shares		49,278
Issuance of ordinary shares upon follow-on public offering, net of issuance cost	280,568	$ 0	280,568
Issuance of ordinary shares upon follow-on public offering, net of issuance cost, Shares		6,300,000
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs	(740)
Share-based compensation	6,463		6,463
Net loss	(47,988)			(47,988)
Foreign currency translation	3,539				3,539
Balance at Mar. 31, 2020	537,588	$ 4	1,022,111	(492,686)	8,159
Balance, Shares at Mar. 31, 2020		74,666,725
Balance at Dec. 31, 2019	294,660	$ 4	734,734	(444,698)	4,620
Balance, Shares at Dec. 31, 2019		68,237,247
Net loss	(128,617)
Foreign currency translation	2,366
Balance at Jun. 30, 2020	465,466	$ 4	1,031,791	(573,315)	6,986
Balance, Shares at Jun. 30, 2020		74,882,338
Balance at Mar. 31, 2020	537,588	$ 4	1,022,111	(492,686)	8,159
Balance, Shares at Mar. 31, 2020		74,666,725
Issuance of ordinary shares upon vesting of restricted shares	0	$ 0	0
Issuance of ordinary shares upon vesting of restricted shares, Shares		36,000
Exercise of shares option	2,729	$ 0	2,729
Exercise of shares option, Shares		179,613
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs	(13)		(13)
Share-based compensation	6,964		6,964
Net loss	(80,629)			(80,629)
Foreign currency translation	(1,173)				(1,173)
Balance at Jun. 30, 2020	465,466	$ 4	1,031,791	(573,315)	6,986
Balance, Shares at Jun. 30, 2020		74,882,338
Balance at Dec. 31, 2020	$ 1,169,345	$ 5	1,897,467	(713,603)	(14,524)
Balance, Shares at Dec. 31, 2020	87,811,026	87,811,026
Issuance of ordinary shares upon vesting of restricted shares	$ 0	$ 0	0
Issuance of ordinary shares upon vesting of restricted shares, Shares		81,600
Exercise of shares option	702	$ 0	702
Exercise of shares option, Shares		58,364
Issuance of ordinary shares in connection with collaboration and license arrangement	62,250	$ 0	62,250
Issuance of ordinary shares in connection with collaboration and license arrangement, Shares		568,182
Issuance cost adjustment for secondary listing	65		65
Share-based compensation	7,318		7,318
Net loss	(232,910)			(232,910)
Foreign currency translation	2,900				2,900
Balance at Mar. 31, 2021	1,009,670	$ 5	1,967,802	(946,513)	(11,624)
Balance, Shares at Mar. 31, 2021		88,519,172
Balance at Dec. 31, 2020	$ 1,169,345	$ 5	1,897,467	(713,603)	(14,524)
Balance, Shares at Dec. 31, 2020	87,811,026	87,811,026
Net loss	$ (396,234)
Foreign currency translation	(2,341)
Balance at Jun. 30, 2021	$ 1,671,698	$ 6	2,799,318	(1,109,837)	(16,865)	$ (924)
Balance, Shares at Jun. 30, 2021	94,758,189	94,758,189				(6,086)
Balance at Mar. 31, 2021	$ 1,009,670	$ 5	1,967,802	(946,513)	(11,624)
Balance, Shares at Mar. 31, 2021		88,519,172
Issuance of ordinary shares upon vesting of restricted shares	0	$ 0	0
Issuance of ordinary shares upon vesting of restricted shares, Shares		32,100
Exercise of shares option	3,289	$ 0	3,289
Exercise of shares option, Shares		490,517
Receipt of employees' shares to satisfy tax withholding obligations related to share-based compensation						(6,086)
Receipt of employees' shares to satisfy tax withholding obligations related to share-based compensation	(924)					$ (924)
Issuance of ordinary shares upon follow-on public offering, net of issuance cost	817,996	$ 1	817,995
Issuance of ordinary shares upon follow-on public offering, net of issuance cost, Shares		5,716,400
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs	(879)
Share-based compensation	10,232		10,232
Net loss	(163,324)			(163,324)
Foreign currency translation	(5,241)				(5,241)
Balance at Jun. 30, 2021	$ 1,671,698	$ 6	$ 2,799,318	$ (1,109,837)	$ (16,865)	$ (924)
Balance, Shares at Jun. 30, 2021	94,758,189	94,758,189				(6,086)