Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 46,742	$ 45,721
Other comprehensive (loss) income, net of tax:
Changes in net prior service credit and actuarial losses	2,506	856
Change in fair value of derivatives	(887)	(390)
Foreign currency translation	(5,242)	13,800
Other comprehensive (loss) income	(3,623)	14,266
Comprehensive income	$ 43,119	$ 59,987