Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 30,955	$ 55,343	$ 77,696	$ 101,067
Other comprehensive income (loss), net of tax:
Changes in net prior service credit and actuarial losses	2,614	778	5,120	1,634
Change in fair value of derivatives	(1,601)	587	(2,488)	197
Foreign currency translation	6,045	(35,621)	803	(21,821)
Other comprehensive income (loss)	7,058	(34,256)	3,435	(19,990)
Comprehensive income	$ 38,013	$ 21,087	$ 81,131	$ 81,077