DEFERRED REVENUE (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2013 T
Deferred Revenue Arrangement [Line Items]
Proceeds from sale of future production	$ 62,000	$ 73,583,000
Volumetric production payment termination date			Dec. 31, 2052
Volumetric production payment estimated percentage sold			10.50%
Volumetric production payment estimated tons to be delivered			15,000,000
Minimum
Deferred Revenue Arrangement [Line Items]
Estimated deferred revenue to be recognized in the next 12 months			1,000,000
Maximum
Deferred Revenue Arrangement [Line Items]
Estimated deferred revenue to be recognized in the next 12 months			$ 1,500,000
Tons subject to volumetric production payment			143,200,000