Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Cost	$ 2,127,675		$ 2,127,675		$ 2,044,819
Accumulated depreciation	(1,320,938)		(1,320,938)		(1,256,879)
Total	806,737		806,737		787,940
Depreciation expense	32,514	$ 34,663	97,625	$ 98,812
Land [Member]
Property, Plant and Equipment [Line Items]
Cost	54,060		54,060		54,918
Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	523,624		523,624		517,049
Machinery, equipment and other [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 1,549,991		$ 1,549,991		$ 1,472,852