Net Income (Loss) 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, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income (loss)	$ 114,801	$ (157,833)	$ 261,898	$ 85,201	$ (43,032)	$ 347,099
Denominator:
Weighted-average ordinary shares used in per share calculation - basic (in shares)	55,413		56,707		55,684	56,955
Dilutive effect of employee equity incentive and purchase plans (in shares)	451		720		0	798
Weighted-average ordinary shares used in per share calculation - diluted (in shares)	55,864		57,427		55,684	57,753
Net income (loss) per ordinary share:
Basic (in dollars per share)	$ 2.07		$ 4.62		$ (0.77)	$ 6.09
Diluted (in dollars per share)	$ 2.06		$ 4.56		$ (0.77)	$ 6.01