Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Cost	$ 2,179,605		$ 2,179,605		$ 2,138,950
Accumulated depreciation	(1,364,602)		(1,364,602)		(1,332,453)
Total	815,003		815,003		806,497
Depreciation expense	33,031	$ 32,947	65,219	$ 65,111
Land [Member]
Property, Plant and Equipment [Line Items]
Cost	50,047		50,047		53,623
Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	513,634		513,634		529,982
Machinery, equipment and other [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 1,615,924		$ 1,615,924		$ 1,555,345