Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 72,951	$ 60,367
Other comprehensive (loss) income:
Foreign currency translation adjustments	2,941	304
Income tax effect		(67)
Foreign currency translation adjustments, net	2,941	237
Pension and other post-retirement adjustments	(99)	(313)
Income tax effect	37	82
Pension and other post-retirement adjustments, net	(62)	(231)
Other comprehensive (loss) income, net of tax	2,879	6
Comprehensive income	$ 75,830	$ 60,373