PROPERTY AND EQUIPMENT (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
PROPERTY AND EQUIPMENT
Total property and equipment	$ 219,730		$ 219,730		$ 204,609
Accumulated depreciation and amortization	(104,446)		(104,446)		(94,817)
Property and equipment, net	115,284		115,284		109,792
Depreciation and amortization expense	3,700	3,400	10,792	10,222
Cell development costs
PROPERTY AND EQUIPMENT
Total property and equipment	65,708		65,708		64,994
Land and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	18,166		18,166		14,920
Buildings and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	56,605		56,605		55,177
Railcars
PROPERTY AND EQUIPMENT
Total property and equipment	17,375		17,375		17,375
Vehicles and other equipment
PROPERTY AND EQUIPMENT
Total property and equipment	42,985		42,985		39,689
Construction in progress
PROPERTY AND EQUIPMENT
Total property and equipment	$ 18,891		$ 18,891		$ 12,454