Quarterly report pursuant to Section 13 or 15(d)

Property And Equipment (Summary Of Oil And Gas Properties Not Subject To Amortization) (Details)

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Property And Equipment (Summary Of Oil And Gas Properties Not Subject To Amortization) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Mar. 31, 2012
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]      
Capitalized costs of oil and natural gas properties excluded from amortization $ 869,879 $ 626,300 $ 626,295
Colorado [Member]
      
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]      
Capitalized costs of oil and natural gas properties excluded from amortization 6,088    
Bakken [Member]
      
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]      
Capitalized costs of oil and natural gas properties excluded from amortization 301    
Southern Louisiana [Member]
      
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]      
Capitalized costs of oil and natural gas properties excluded from amortization 789    
Ohio [Member]
      
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]      
Capitalized costs of oil and natural gas properties excluded from amortization 862,655    
Other [Member]
      
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]      
Capitalized costs of oil and natural gas properties excluded from amortization $ 46