Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 71,980	$ 68,044
Less: Accumulated depreciation	60,697	59,404
Property, plant and equipment, excluding construction in progress, net	11,283	8,640
Construction in progress	493	352
Total	11,776	8,992
Depreciation expense	1,900	2,100	$ 2,800
Railroad and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	33,626	33,626
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	22,552	19,191
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	9,468	8,998
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,322	5,154
Autos and trucks
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,012	$ 1,075