Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,841,671	$ 2,057,656	$ 1,987,111
Amortization	21,077	20,486	19,041
Other current period change	(124,328)	106,045	(140,338)
Adoption of new accounting standard	(100,567)		20,396
Ending balance	2,910,327	2,841,671	2,057,656
Currency Translation Adjustments and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(140,438)	(206,610)	(136,020)
Amortization	0	0	0
Other current period change	(58,960)	66,172	(70,590)
Ending balance	(199,398)	(140,438)	(206,610)
Net Actuarial Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(560,153)	(620,292)	(576,993)
Amortization	20,773	20,267	18,876
Other current period change	(62,017)	39,872	(62,175)
Adoption of new accounting standard	(98,987)
Ending balance	(700,384)	(560,153)	(620,292)
Prior Service Credit
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6,910)	(7,130)	278
Amortization	304	219	165
Other current period change	(3,351)	1	(7,573)
Adoption of new accounting standard	(1,580)
Ending balance	(11,537)	(6,910)	(7,130)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(707,501)	(834,032)	(712,735)
Ending balance	$ (911,319)	$ (707,501)	$ (834,032)