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
Jun. 30, 2013
Dec. 31, 2012
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Capitalized costs of oil and natural gas properties excluded from amortization $ 872,113 $ 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 6,153  
Bakken [Member]
    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Capitalized costs of oil and natural gas properties excluded from amortization 307  
Southern Louisiana [Member]
    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Capitalized costs of oil and natural gas properties excluded from amortization 893  
Ohio [Member]
    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Capitalized costs of oil and natural gas properties excluded from amortization 864,710  
Other [Member]
    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Capitalized costs of oil and natural gas properties excluded from amortization $ 50