Quarterly report pursuant to Section 13 or 15(d)

CRUDE OIL AND NATURAL GAS PROPERTIES (Details)

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CRUDE OIL AND NATURAL GAS PROPERTIES (Details) (USD $)
9 Months Ended 12 Months Ended
Sep. 30, 2013
acre
Project
PlannedWells
Sep. 30, 2012
acre
Dec. 31, 2012
acre
Acquisitions [Abstract]      
Capital expenditures incurred but not yet paid $ 136,400,000   $ 91,800,000
Mineral acres acquired, net (in acres) 17,854 21,153  
Average acquisition cost per net acre 1,234 1,913  
Productive oil and gas wells, Number of wells, Gross 56    
Productive oil and gas wells, Number of wells, Net 5.5    
Productive Oil and Gas Wells, Cost 7,300,000    
Unproved Properties [Abstract]      
Unproven leasehold interests (in net acres) 64,500   64,500
Anticipated future period over which excluded costs will become subject to depletion 5 years    
Capitalized costs as of the balance sheet date that have been excluded $ 85,100,000   $ 82,900,000
Number of defined drilling projects participating with Slawson 3    
Slawson Projects [Member]
     
Unproved Properties [Abstract]      
Percentage of participation interests, minimum (in hundredths) 4.50%    
Percentage of participation interests, maximum (in hundredths) 50.00%    
Aggregate acres of leasehold interest held 19,600    
Windsor Project Area [Member]
     
Unproved Properties [Abstract]      
Percentage of participation interests (in hundredths) 4.50%    
Aggregate acres of leasehold interest held 2,100    
South West Big Sky Project [Member]
     
Unproved Properties [Abstract]      
Percentage of participation interests (in hundredths) 20.00%    
Aggregate acres of leasehold interest held 5,500    
Lambert Project [Member]
     
Unproved Properties [Abstract]      
Percentage of participation interests (in hundredths) 50.00%    
Aggregate acres of leasehold interest held 12,000