Property, Plant & Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 2,497,735	$ 2,219,925
Less: accumulated depreciation	1,282,952	1,192,694
Property, plant and equipment, net	1,214,783	1,027,231	$ 936,702
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	128,353	105,960
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	789,359	724,781
Machinery, equipment and other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 1,580,023	$ 1,389,184