Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 69,770	$ 70,316	$ 129,655	$ 145,866
Other comprehensive income (loss), net of tax:
Changes in net prior service credit and actuarial losses	4,181	12	5,992	1,632
Change in fair value of derivatives	228	(277)	689	(107)
Foreign currency translation	2,625	(13,834)	6,863	(32,779)
Other comprehensive income (loss)	7,034	(14,099)	13,544	(31,254)
Comprehensive income	$ 76,804	$ 56,217	$ 143,199	$ 114,612