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				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income	$ 261,898	$ 85,201	$ 92,321	$ 45,991	$ 347,099	$ 138,312
Denominator:
Weighted-average ordinary shares used in per share calculation - basic (in shares)	56,707		60,177		56,955	60,053
Dilutive effect of employee equity incentive and purchase plans (in shares)	720		1,261		798	1,256
Weighted-average ordinary shares used in per share calculation - diluted (in shares)	57,427		61,438		57,753	61,309
Net income per ordinary share:
Basic (in dollars per share)	$ 4.62		$ 1.53		$ 6.09	$ 2.30
Diluted (in dollars per share)	$ 4.56		$ 1.50		$ 6.01	$ 2.26