Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Ordinary shares	Additional paid-in capital	Accumulated other comprehensive income (loss)	Retained earnings (accumulated deficit)
Beginning balance at Dec. 31, 2016	$ 142,345		$ 664,154	$ (1,883)	$ (519,926)
Beginning balance (in shares) at Dec. 31, 2016		87,066,446
Share-based compensation to employees	27,116		27,116
Exercise of options and warrants	3,685		3,685
Exercise of options and warrants (in shares)		2,244,153
Issuance of shares in connection with employee stock purchase plan	1,540		1,540
Issuance of shares in connection with employee stock purchase plan (in shares)		167,433
Tax benefit from share-based award activity	0		670		(670)
Other comprehensive income (loss), net of tax (benefit) expense	540			540
Net income (loss)	(61,662)				(61,662)
Ending balance at Dec. 31, 2017	113,564		697,165	(1,343)	(582,258)
Ending balance (in shares) at Dec. 31, 2017		89,478,032
Share-based compensation to employees	39,846		39,846
Exercise of options and warrants	18,468		18,468
Exercise of options and warrants (in shares)		3,688,781
Issuance of shares in connection with employee stock purchase plan	1,835		1,835
Issuance of shares in connection with employee stock purchase plan (in shares)		87,372
Other comprehensive income (loss), net of tax (benefit) expense	(57)			(57)
Net income (loss)	(63,559)				(63,559)
Ending balance at Dec. 31, 2018	112,259		757,314	(1,400)	(643,655)
Ending balance (in shares) at Dec. 31, 2018		93,254,185
Share-based compensation to employees	52,416		52,416
Exercise of options and warrants	59,245		59,245
Exercise of options and warrants (in shares)		6,206,884
Proceeds from issuance of shares	2,467		2,467
Proceeds from issuance of shares (in shares)		67,366
Other comprehensive income (loss), net of tax (benefit) expense	(1,367)			(1,367)
Net income (loss)	(7,230)				(7,230)
Ending balance at Dec. 31, 2019	$ 217,790		$ 871,442	$ (2,767)	$ (650,885)
Ending balance (in shares) at Dec. 31, 2019		99,528,435