Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 316,132	$ 321,406	$ 333,948
Other comprehensive loss:
Foreign currency translation adjustments	(14,081)	(22,872)	(15,349)
Change in unrealized loss on investments, net of income tax benefit of $432, $773 and $689 for the years ended December 31, 2016, 2015 and 2014, respectively	(688)	(970)	(171)
Other comprehensive loss	(14,769)	(23,842)	(15,520)
Comprehensive income	$ 301,363	$ 297,564	$ 318,428