PROPERTY AND EQUIPMENT (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
PROPERTY AND EQUIPMENT
Total property and equipment	$ 226,000		$ 221,540
Accumulated depreciation and amortization	(109,581)		(106,681)
Property and equipment, net	116,419		114,859
Depreciation and amortization expense	3,839	3,439
Cell development costs
PROPERTY AND EQUIPMENT
Total property and equipment	81,004		77,348
Land and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	17,967		18,073
Buildings and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	58,515		59,101
Railcars
PROPERTY AND EQUIPMENT
Total property and equipment	17,375		17,375
Vehicles and other equipment
PROPERTY AND EQUIPMENT
Total property and equipment	43,847		42,859
Construction in progress
PROPERTY AND EQUIPMENT
Total property and equipment	$ 7,292		$ 6,784