Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment
Gross property, plant and equipment	$ 1,852,394	$ 1,757,486
Less: Accumulated depreciation	(1,373,253)	(1,267,231)
Property, plant and equipment, net	479,141	490,255
Land
Property, Plant and Equipment
Gross property, plant and equipment	10,965	10,606
Land improvements
Property, Plant and Equipment
Gross property, plant and equipment	15,567	15,032
Buildings and improvements
Property, Plant and Equipment
Gross property, plant and equipment	195,739	185,657
Machinery and equipment
Property, Plant and Equipment
Gross property, plant and equipment	1,606,633	1,525,156
Construction in progress
Property, Plant and Equipment
Gross property, plant and equipment	$ 23,490	$ 21,035