Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Components of Property, plant and equipment
Property, plant and equipment, gross	$ 672,906		$ 673,548
Less accumulated depreciation	(125,834)		(117,067)
Property, plant and equipment excluding construction in progress	547,072		556,481
Construction in progress	6,021		5,849
Total property, plant and equipment, net	553,093	$ 587,680	562,330
Total depreciation expense	9,300	$ 9,300
Land
Components of Property, plant and equipment
Property, plant and equipment, gross	13,492		13,492
Land improvements
Components of Property, plant and equipment
Property, plant and equipment, gross	42,962		42,962
Buildings
Components of Property, plant and equipment
Property, plant and equipment, gross	196,155		196,153
Machinery and equipment
Components of Property, plant and equipment
Property, plant and equipment, gross	412,652		413,349
Vehicles
Components of Property, plant and equipment
Property, plant and equipment, gross	635		635
Furniture and office equipment
Components of Property, plant and equipment
Property, plant and equipment, gross	6,023		5,970
Leasehold improvements.
Components of Property, plant and equipment
Property, plant and equipment, gross	$ 987		$ 987