Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Components of property, plant and equipment
Land	$ 23,342	$ 30,672	$ 28,473
Land improvements and leasehold improvements	71,559	79,631	82,908
Buildings and storage facilities	298,951	322,856	319,950
Machinery and equipment	384,422	392,418	393,178
Construction in progress	7,703	12,784	21,284
Property, plant and equipment, gross	785,977	838,361	845,793
Less: accumulated depreciation	366,629	388,309	385,546
Property, plant and equipment, net	$ 419,348	$ 450,052	$ 460,247