Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
COMPREHENSIVE INCOME:
Net income	$ 290,584	$ 343,389	$ 357,796
Foreign currency translation adjustments, net of tax	24,009	(10,208)	(25,024)
Total comprehensive income	$ 314,593	$ 333,181	$ 332,772