Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment
Gross property, plant and equipment	$ 2,008,655	$ 2,186,407
Less: Accumulated depreciation	(1,424,948)	(1,523,163)
Property, plant and equipment, net	583,707	663,244
Land
Property, Plant and Equipment
Gross property, plant and equipment	11,065	15,721
Land improvements
Property, Plant and Equipment
Gross property, plant and equipment	15,408	15,898
Buildings and improvements
Property, Plant and Equipment
Gross property, plant and equipment	201,213	205,409
Machinery and equipment
Property, Plant and Equipment
Gross property, plant and equipment	1,725,312	1,861,965
Uncompleted construction
Property, Plant and Equipment
Gross property, plant and equipment	$ 55,657	$ 87,414