The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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PROPERTY AND EQUIPMENT (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
PROPERTY AND EQUIPMENT
Total property and equipment	$ 210,866		$ 204,609
Accumulated depreciation and amortization	(97,547)		(94,817)
Property and equipment, net	113,319		109,792
Depreciation expense	3,439	3,223
Cell development costs
PROPERTY AND EQUIPMENT
Total property and equipment	64,905		64,994
Land and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	18,152		14,920
Buildings and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	55,960		55,177
Railcars
PROPERTY AND EQUIPMENT
Total property and equipment	17,375		17,375
Vehicles and other equipment
PROPERTY AND EQUIPMENT
Total property and equipment	40,129		39,689
Construction in progress
PROPERTY AND EQUIPMENT
Total property and equipment	$ 14,345		$ 12,454