Property, Plant and Equipment (Components) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Land	$ 25,500	$ 35,700
Buildings and improvements	210,900	234,400
Machinery and equipment	838,600	804,400
Capital leases	49,900	27,500
Construction in progress and equipment not yet in service	61,900	70,000
Total	1,186,800	1,172,000
Less accumulated depreciation	(778,550)	(774,200)
Property, plant and equipment, net	$ 408,300	$ 397,800	$ 361,400