Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 43,061	$ 56,752	$ 96,775	$ 131,335
Other comprehensive (loss) income:
Foreign currency translation adjustments	(24,558)	13,568	(18,275)	23,495
Change in unrealized gain (loss) on investments, net of income tax (provision) benefit of $(299), $(193), $572 and $(681) for the three and six months ended June 30, 2018 and 2017, respectively	921	320	(1,765)	1,130
Other comprehensive (loss) income	(23,637)	13,888	(20,040)	24,625
Comprehensive income	$ 19,424	$ 70,640	$ 76,735	$ 155,960