Net Income per Ordinary Share - Basic and Diluted Net Income (Loss) per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income	$ 102,276	$ 261,898	$ 85,201	$ 149,316	$ 92,321	$ 45,991	$ 449,375	$ 287,628
Denominator:
Weighted-average ordinary shares used in per share calculation - basic (in shares)	56,674			60,476			56,860	60,196
Dilutive effect of employee equity incentive and purchase plans (in shares)	764			1,381			787	1,297
Weighted-average ordinary shares used in per share calculation - diluted (in shares)	57,438			61,857			57,647	61,493
Net income per ordinary share:
Basic (in dollars per share)	$ 1.80			$ 2.47			$ 7.90	$ 4.78
Diluted (in dollars per share)	$ 1.78			$ 2.41			$ 7.80	$ 4.68