Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 2,052,275
Amortization	15,417	$ 14,186
Other current period change	71,801	(48,896)
Ending balance	2,175,064
Currency Translation Adjustments and Other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(206,610)	(136,020)
Amortization	0	0
Other current period change	70,991	(37,874)
Ending balance	(135,619)	(173,894)
Net Actuarial Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(620,292)	(576,993)
Amortization	15,252	14,052
Other current period change	810	(5,495)
Ending balance	(604,230)	(568,436)
Prior Service (Cost)/ Credit
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(7,130)	278
Amortization	165	134
Other current period change	0	(5,527)
Ending balance	(6,965)	(5,115)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(834,032)	(712,735)
Ending balance	$ (746,814)	$ (747,445)