CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Treasury Stock
BALANCE at Dec. 31, 2016	$ 1,209,481	$ 1,539	$ 2,231,797	$ (3,274)	$ (947,942)	$ (72,639)
BALANCE (in shares) at Dec. 31, 2016		154,191,281				(1,760,767)
Issuance of ordinary shares under employee stock plans	23,517	$ 16	23,501
Issuance of ordinary shares under employee stock plans (in shares)		1,850,084
Receipt of Alkermes' shares for the purchase of stock options or to satisfy minimum tax withholding obligations related to share-based awards	(16,433)	$ 2	273			$ (16,708)
Receipt of Alkermes' shares for the purchase of stock options or to satisfy minimum tax withholding obligations related to share based awards (in shares)		16,267				(287,409)
Share-based compensation expense	83,184		83,184
Unrealized gain (loss) on marketable securities, net of tax provision (benefit)	(518)			(518)
Cumulative effect adjustment related to change in accounting for excess tax benefits	61,522				61,522
Net loss	(157,945)				(157,945)
BALANCE at Dec. 31, 2017	1,202,808	$ 1,557	2,338,755	(3,792)	(1,044,365)	$ (89,347)
BALANCE (in shares) at Dec. 31, 2017		156,057,632				(2,048,176)
Issuance of ordinary shares under employee stock plans	20,877	$ 11	20,866
Issuance of ordinary shares under employee stock plans (in shares)		1,087,815
Receipt of Alkermes' shares for the purchase of stock options or to satisfy minimum tax withholding obligations related to share-based awards	(19,622)	$ 11	(11)			$ (19,622)
Receipt of Alkermes' shares for the purchase of stock options or to satisfy minimum tax withholding obligations related to share based awards (in shares)		1,035,386				(375,313)
Share-based compensation expense	107,713		107,713
Unrealized gain (loss) on marketable securities, net of tax provision (benefit)	512			512
Cumulative effect adjustment related to the adoption of new accounting standards	(1,692)				(1,692)
Net loss	(139,311)				(139,311)
BALANCE at Dec. 31, 2018	1,171,285	$ 1,579	2,467,323	(3,280)	(1,185,368)	$ (108,969)
BALANCE (in shares) at Dec. 31, 2018		158,180,833				(2,423,489)
Issuance of ordinary shares under employee stock plans	18,925	$ 15	18,910
Issuance of ordinary shares under employee stock plans (in shares)		1,510,177
Receipt of Alkermes' shares for the purchase of stock options or to satisfy minimum tax withholding obligations related to share-based awards	(9,317)	$ 8	92			$ (9,417)
Receipt of Alkermes' shares for the purchase of stock options or to satisfy minimum tax withholding obligations related to share based awards (in shares)		798,878				(287,397)
Share-based compensation expense	99,705		99,705
Unrealized gain (loss) on marketable securities, net of tax provision (benefit)	1,464			1,464
Net loss	(196,620)				(196,620)
BALANCE at Dec. 31, 2019	$ 1,085,442	$ 1,602	$ 2,586,030	$ (1,816)	$ (1,381,988)	$ (118,386)
BALANCE (in shares) at Dec. 31, 2019		160,489,888				(2,710,886)