CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' DEFICIT - USD ($) shares in Thousands, $ in Thousands	Ordinary Shares	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Balances at Dec. 31, 2020	$ 1	$ 1,222,818	$ 47	$ (1,526,617)	$ (303,751)
Balances (in shares) at Dec. 31, 2020	64,328
Increase (Decrease) in Stockholders' Equity
Net proceeds from sale of ordinary shares		108,180			108,180
Net proceeds from sale of ordinary shares (in shares)	7,705
Proceeds from ESPP purchases		2,862			2,862
Proceeds from ESPP purchases (in shares)	189
Employee share-based compensation expense		30,773			30,773
Issuance of restricted shares (in shares)	1,587
Option exercises		5			5
Repurchase of shares to satisfy tax withholding		(6,320)			(6,320)
Repurchase of shares to satisfy tax withholding (in shares)	(339)
Net unrealized gain (loss) on marketable securities			(39)		(39)
Net loss				(132,084)	(132,084)
Balances at Jun. 30, 2021	$ 1	1,358,318	8	(1,658,701)	(300,374)
Balances (in shares) at Jun. 30, 2021	73,470
Balances at Mar. 31, 2021	$ 1	1,233,060	17	(1,606,296)	(373,218)
Balances (in shares) at Mar. 31, 2021	65,218
Increase (Decrease) in Stockholders' Equity
Net proceeds from sale of ordinary shares		108,180			108,180
Net proceeds from sale of ordinary shares (in shares)	7,705
Proceeds from ESPP purchases		2,862			2,862
Proceeds from ESPP purchases (in shares)	189
Employee share-based compensation expense		14,941			14,941
Issuance of restricted shares (in shares)	399
Option exercises		2			2
Repurchase of shares to satisfy tax withholding		(727)			(727)
Repurchase of shares to satisfy tax withholding (in shares)	(41)
Net unrealized gain (loss) on marketable securities			(9)		(9)
Net loss				(52,405)	(52,405)
Balances at Jun. 30, 2021	$ 1	1,358,318	8	(1,658,701)	(300,374)
Balances (in shares) at Jun. 30, 2021	73,470
Balances at Dec. 31, 2021	$ 1	1,387,469		(1,726,043)	$ (338,573)
Balances (in shares) at Dec. 31, 2021	74,435				74,435
Increase (Decrease) in Stockholders' Equity
Proceeds from ESPP purchases		487			$ 487
Proceeds from ESPP purchases (in shares)	72
Employee share-based compensation expense		24,254			24,254
Issuance of restricted shares (in shares)	2,109
Repurchase of shares to satisfy tax withholding		(1,795)			(1,795)
Repurchase of shares to satisfy tax withholding (in shares)	(189)
Net unrealized gain (loss) on marketable securities			(45)		(45)
Net loss				(34,137)	(34,137)
Balances at Jun. 30, 2022	$ 1	1,410,415	(45)	(1,760,180)	$ (349,809)
Balances (in shares) at Jun. 30, 2022	76,427				76,427
Balances at Mar. 31, 2022	$ 1	1,400,566	(28)	(1,751,989)	$ (351,450)
Balances (in shares) at Mar. 31, 2022	76,081
Increase (Decrease) in Stockholders' Equity
Proceeds from ESPP purchases		487			487
Proceeds from ESPP purchases (in shares)	72
Employee share-based compensation expense		9,709			9,709
Issuance of restricted shares (in shares)	313
Repurchase of shares to satisfy tax withholding		(347)			(347)
Repurchase of shares to satisfy tax withholding (in shares)	(39)
Net unrealized gain (loss) on marketable securities			(17)		(17)
Net loss				(8,191)	(8,191)
Balances at Jun. 30, 2022	$ 1	$ 1,410,415	$ (45)	$ (1,760,180)	$ (349,809)
Balances (in shares) at Jun. 30, 2022	76,427				76,427