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Commitments and Contingencies - Additional Information (Details) (USD $)
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Commitments and Contingencies Disclosure [Line Items]      
Total rental expense under operating leases $ 3,600,000 $ 2,600,000 $ 1,500,000
Permian Trust
      
Commitments and Contingencies Disclosure [Line Items]      
Development period deadline under development agreement latest date Mar. 31, 2016    
Mississippian Trust II
      
Commitments and Contingencies Disclosure [Line Items]      
Development period deadline under development agreement latest date Dec. 31, 2016    
Permian Trust and Mississippian Trust II
      
Commitments and Contingencies Disclosure [Line Items]      
Estimated remaining drilling obligation 137,000,000    
Gas Gathering Agreement | Pinon Gathering Company LLC
      
Commitments and Contingencies Disclosure [Line Items]      
Agreement expiration date Jun. 30, 2029    
Treating Agreement
      
Commitments and Contingencies Disclosure [Line Items]      
Contract agreement, term 30 years    
Minimum delivery required (in Bcf) 3,200    
Estimated minimum delivery required remaining (in Bcf) 3,000    
Initial shortfall price, per Mcf 0.25    
Shortfall price, per Mcf, final year of agreement 0.70    
Accrued shortfall 32,700,000    
Treating Agreement | Minimum
      
Commitments and Contingencies Disclosure [Line Items]      
Range of projected shortfall in one year 30,000,000    
Treating Agreement | Maximum
      
Commitments and Contingencies Disclosure [Line Items]      
Range of projected shortfall in one year 37,000,000    
Patriot Exploration, LLC, Jonathan Feldman, Redwing Drilling Partners, Mapleleaf Drilling Partners, Avalanche Drilling Partners, Penguin Drilling Partners and Gramax Insurance Company Ltd.
      
Commitments and Contingencies Disclosure [Line Items]      
Plaintiffs investment under participation agreement 16,000,000    
General Land Office of the State of Texas
      
Commitments and Contingencies Disclosure [Line Items]      
Loss contingency, damages sought, value 13,000,000    
Wesley West Minerals, Ltd and Longfellow Ranch Partners, LP
      
Commitments and Contingencies Disclosure [Line Items]      
Loss contingency, damages sought, value 45,500,000    
Rig Commitments
      
Commitments and Contingencies Disclosure [Line Items]      
Minimum future commitments, 2014 20,300,000    
Minimum future commitments, 2015 $ 1,100,000