Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 76,000	$ 88,040	$ 224,493	$ 232,986
Other comprehensive (loss) income:
Foreign currency translation adjustments	(358)	(9,261)	5,567	(17,069)
Change in unrealized (loss) gain on investments, net of income tax benefit (provision) of $867, $(73), $(1,445)and $(647) for the three and nine months ended September 30, 2016 and 2015, respectively	(1,488)	121	2,424	1,161
Other comprehensive (loss) income	(1,846)	(9,140)	7,991	(15,908)
Comprehensive income	$ 74,154	$ 78,900	$ 232,484	$ 217,078