Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 269,659	$ 153,351	$ 172,413
Other comprehensive income (loss), net of tax:
Changes in net prior service credit and net actuarial losses, net of tax benefit (provision) of $3,017, $(1,786) and $(1,960), respectively	(6,293)	1,175	4,972
Change in fair value of derivatives, net of tax benefit (provision) of $355, $(906) and $(129), respectively	(613)	1,528	210
Foreign currency translation, net of tax benefit (provision) of $17,131, $(2,829) and $(9,949), respectively	63,874	(17,753)	(48,364)
Other comprehensive income (loss)	56,968	(15,050)	(43,182)
Comprehensive income	$ 326,627	$ 138,301	$ 129,231