Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Ordinary Shares [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2018	$ 1,190,106	$ 17	$ (4,585)	$ 2,374,966	$ (1,523)	$ (1,178,769)
Beginning balance, shares at Dec. 31, 2018		169,244,520	384,366
Cumulative effect adjustments from adoption of ASU 2016-02	64					64
Issuance of ordinary shares - public offering	326,849	$ 1		326,848
Issuance of ordinary shares - public offering, shares		14,081,632
Issuance of ordinary shares in conjunction with vesting of restricted stock units, performance stock units and stock option exercises	10,042			10,042
Issuance of ordinary shares in conjunction with vesting of restricted stock units, performance stock units and stock option exercises, shares		1,804,196
Ordinary shares withheld for payment of employees’ withholding tax liability	(17,171)			(17,171)
Share-based compensation	27,548			27,548
Currency translation adjustment	(487)				(487)
Net loss	(32,863)					(32,863)
Ending balance at Mar. 31, 2019	1,504,088	$ 18	$ (4,585)	2,722,233	(2,010)	(1,211,568)
Ending balance, shares at Mar. 31, 2019		185,130,348	384,366
Beginning balance at Dec. 31, 2019	2,185,449	$ 19	$ (4,585)	2,797,602	(1,905)	(605,682)
Beginning balance, shares at Dec. 31, 2019		188,402,040	384,366
Issuance of ordinary shares in conjunction with vesting of restricted stock units, performance stock units and stock option exercises	7,049			7,049
Issuance of ordinary shares in conjunction with vesting of restricted stock units, performance stock units and stock option exercises, shares		2,560,573
Ordinary shares withheld for payment of employees’ withholding tax liability	(46,664)			(46,664)
Share-based compensation	56,421			56,421
Currency translation adjustment	(325)				(325)
Net loss	(13,591)					(13,591)
Ending balance at Mar. 31, 2020	$ 2,188,339	$ 19	$ (4,585)	$ 2,814,408	$ (2,230)	$ (619,273)
Ending balance, shares at Mar. 31, 2020		190,962,613	384,366