CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Ordinary Shares	Non-voting Euro Deferred	Capital Redemption Reserve	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2018		57,504	4,000
Beginning balance at Dec. 31, 2018	$ 2,757,422	$ 6	$ 55	$ 472	$ 2,113,630	$ (197,791)	$ 841,050
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Issuance of ordinary shares in conjunction with exercise of share options (in shares)		54
Issuance of ordinary shares in conjunction with exercise of share options	3,057				3,057
Issuance of ordinary shares in conjunction with vesting of restricted stock units (in shares)		203
Shares withheld for payment of employee's withholding tax liability	(13,810)				(13,810)
Share-based compensation	27,861				27,861
Shares repurchased (in shares)		(858)
Shares repurchased	(111,249)						(111,249)
Other comprehensive loss	(22,883)					(22,883)
Net income (loss)	85,201						85,201
Ending balance (in shares) at Mar. 31, 2019		56,903	4,000
Ending balance at Mar. 31, 2019	2,730,447	$ 6	$ 55	472	2,130,738	(220,674)	819,850
Beginning balance (in shares) at Dec. 31, 2019		56,140	4,000
Beginning balance at Dec. 31, 2019	3,110,981	$ 6	$ 55	472	2,266,026	(223,393)	1,067,815
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Issuance of ordinary shares in conjunction with exercise of share options (in shares)		145
Issuance of ordinary shares in conjunction with exercise of share options	13,264				13,264
Issuance of ordinary shares in conjunction with vesting of restricted stock units (in shares)		214
Shares withheld for payment of employee's withholding tax liability	(13,547)				(13,547)
Share-based compensation	28,731				28,731
Shares repurchased (in shares)		(1,131)
Shares repurchased	(139,053)						(139,053)
Other comprehensive loss	(34,043)					(34,043)
Net income (loss)	(157,833)						(157,833)
Ending balance (in shares) at Mar. 31, 2020		55,368	4,000
Ending balance at Mar. 31, 2020	$ 2,808,500	$ 6	$ 55	$ 472	$ 2,294,474	$ (257,436)	$ 770,929