Property and Equipment, Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 68,044	$ 66,919
Less: Accumulated depreciation	59,404	57,103
Property, plant and equipment, excluding construction in progress, net	8,640	9,816
Construction in progress	352	329
Total	8,992	10,145
Depreciation expense	2,100	2,800	$ 2,200
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	19,191	16,749
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,998	9,900
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,154	5,600
Autos and trucks
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,075	$ 1,044