Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified			12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Minimum	Dec. 31, 2012 Maximum	Dec. 31, 2012 Rail road property and equipment	Dec. 31, 2011 Rail road property and equipment	Dec. 31, 2012 Rail road property and equipment Minimum	Dec. 31, 2012 Rail road property and equipment Maximum	Dec. 31, 2012 Machinery and Equipment	Dec. 31, 2011 Machinery and Equipment	Dec. 31, 2012 Machinery and Equipment Minimum	Dec. 31, 2012 Machinery and Equipment Maximum	Dec. 31, 2012 Office equipment	Dec. 31, 2011 Office equipment	Dec. 31, 2012 Office equipment Minimum	Dec. 31, 2012 Office equipment Maximum	Dec. 31, 2012 Autos and trucks	Dec. 31, 2011 Autos and trucks	Dec. 31, 2012 Autos and trucks Minimum	Dec. 31, 2012 Autos and trucks Maximum
Property, Plant, and Equipment Disclosure [Line Items]
Property and equipment, gross	$ 49,393	$ 50,914			$ 10,140	$ 10,140			$ 18,618	$ 18,978			$ 18,909	$ 19,845			$ 1,726	$ 1,951
Less: Accumulated depreciation	37,614	36,514
Property, plant and equipment, excluding construction in progress, net	11,779	14,400
Construction in progress	370	546
Total	$ 12,149	$ 14,946
Estimated Useful Life (in years)			3 years	30 years			15 years	30 years			3 years	10 years			3 years	10 years			3 years	10 years