CRUDE OIL AND NATURAL GAS PROPERTIES (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
CRUDE OIL AND NATURAL GAS PROPERTIES [Abstract]
Capital expenditures incurred but not yet paid	$ 138,700,000
Acquisitions [Abstract]
Mineral acres acquired, net (in acres)	17,338	24,281
Average Acquisition Cost Per Net Acre	1,881	1,808
Unproved Properties [Abstract]
Gas and Oil Acreage, Undeveloped, Net Acres	74,000		117,000
Anticipated future period over which excluded costs will become subject to depletion (in years)	5
Wells In Process Of Drilling Gross	150
Wells In Process Of Drilling Net	10.8
Amount of capitalized costs excluded from depletion	$ 98,100,000		$ 137,800,000
Number of defined drilling projects participating with Slawson	3
Aggregate acres of leasehold interest held	18,540
Windsor Project Area [Member]
Unproved Properties [Abstract]
Aggregate acres of leasehold interest held	2,722
South West Big Sky Project [Member]
Unproved Properties [Abstract]
Aggregate acres of leasehold interest held	4,525
Lambert Project [Member]
Unproved Properties [Abstract]
Aggregate acres of leasehold interest held	11,293