Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 80,930	$ 74,858
Other comprehensive income:
Foreign currency translation adjustments	9,499	9,653
Change in unrealized gain on investments, net of income tax provision of $488 and $1,783 for the three months ended March 31, 2017 and 2016, respectively	810	3,008
Other comprehensive income	10,309	12,661
Comprehensive income	$ 91,239	$ 87,519