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	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment 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	$ 4,848	$ 4,848
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 (loss) income	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, 2018		57,504	4,000
Beginning balance at Dec. 31, 2018	2,757,422	$ 6	$ 55	472	2,113,630	(197,791)	841,050	$ 4,848	$ 4,848
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Other comprehensive loss	(61,651)
Net (loss) income	449,375
Ending balance (in shares) at Sep. 30, 2019		56,619	4,000
Ending balance at Sep. 30, 2019	3,054,405	$ 6	$ 55	472	2,209,156	(259,442)	1,104,158
Beginning balance (in shares) at Mar. 31, 2019		56,903	4,000
Beginning balance at Mar. 31, 2019	2,730,447	$ 6	$ 55	472	2,130,738	(220,674)	819,850
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Issuance of ordinary shares in conjunction with exercise of share options (in shares)		98
Issuance of ordinary shares in conjunction with exercise of share options	7,033				7,033
Issuance of ordinary shares under employee stock purchase plan (in shares)		57
Issuance of ordinary shares under employee stock purchase plan	6,032				6,032
Issuance of ordinary shares in conjunction with vesting of restricted stock units (in shares)		15
Shares withheld for payment of employee's withholding tax liability	(1,003)				(1,003)
Share-based compensation	28,658				28,658
Shares repurchased (in shares)		(447)
Shares repurchased	(59,869)						(59,869)
Other comprehensive loss	10,238					10,238
Net (loss) income	261,898						261,898
Ending balance (in shares) at Jun. 30, 2019		56,626	4,000
Ending balance at Jun. 30, 2019	2,983,434	$ 6	$ 55	472	2,171,458	(210,436)	1,021,879
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Issuance of ordinary shares in conjunction with exercise of share options (in shares)		110
Issuance of ordinary shares in conjunction with exercise of share options	9,968				9,968
Issuance of ordinary shares in conjunction with vesting of restricted stock units (in shares)		32
Shares withheld for payment of employee's withholding tax liability	(1,087)				(1,087)
Share-based compensation	28,817				28,817
Shares repurchased (in shares)		(149)
Shares repurchased	(19,997)						(19,997)
Other comprehensive loss	(49,006)					(49,006)
Net (loss) income	102,276						102,276
Ending balance (in shares) at Sep. 30, 2019		56,619	4,000
Ending balance at Sep. 30, 2019	3,054,405	$ 6	$ 55	472	2,209,156	(259,442)	1,104,158
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 (loss) income	(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
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]
Other comprehensive loss	35,592
Net (loss) income	105,202
Ending balance (in shares) at Sep. 30, 2020		55,592	4,000
Ending balance at Sep. 30, 2020	3,377,201	$ 6	$ 55	472	2,537,989	(187,801)	1,026,480
Beginning balance (in shares) at Mar. 31, 2020		55,368	4,000
Beginning balance at Mar. 31, 2020	2,808,500	$ 6	$ 55	472	2,294,474	(257,436)	770,929
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Issuance of Exchangeable Senior Notes, due 2026	176,260				176,260
Partial repurchase of Exchangeable Senior Notes, due 2021	(12,069)				(12,069)
Issuance of ordinary shares in conjunction with exercise of share options (in shares)		74
Issuance of ordinary shares in conjunction with exercise of share options	4,440				4,440
Issuance of ordinary shares under employee stock purchase plan (in shares)		65
Issuance of ordinary shares under employee stock purchase plan	6,547				6,547
Issuance of ordinary shares in conjunction with vesting of restricted stock units (in shares)		19
Shares withheld for payment of employee's withholding tax liability	(1,116)				(1,116)
Share-based compensation	30,599				30,599
Shares repurchased (in shares)		(70)
Shares repurchased	(7,484)						(7,484)
Other comprehensive loss	21,327					21,327
Net (loss) income	114,801						114,801
Ending balance (in shares) at Jun. 30, 2020		55,456	4,000
Ending balance at Jun. 30, 2020	3,141,805	$ 6	$ 55	472	2,499,135	(236,109)	878,246
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Partial repurchase of Exchangeable Senior Notes, due 2021	(444)				(444)
Issuance of ordinary shares in conjunction with exercise of share options (in shares)		96
Issuance of ordinary shares in conjunction with exercise of share options	10,088				10,088
Issuance of ordinary shares in conjunction with vesting of restricted stock units (in shares)		40
Shares withheld for payment of employee's withholding tax liability	(1,097)				(1,097)
Share-based compensation	30,307				30,307
Other comprehensive loss	48,308					48,308
Net (loss) income	148,234						148,234
Ending balance (in shares) at Sep. 30, 2020		55,592	4,000
Ending balance at Sep. 30, 2020	$ 3,377,201	$ 6	$ 55	$ 472	$ 2,537,989	$ (187,801)	$ 1,026,480