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
Jun. 30, 2017
Dec. 31, 2016
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Total oil and gas properties not subject to amortization, total $ 3,109,143 $ 1,580,305
Utica    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Total oil and gas properties not subject to amortization, total 1,614,824  
MidCon    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Total oil and gas properties not subject to amortization, total 1,491,144  
Niobrara    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Total oil and gas properties not subject to amortization, total 2,173  
Southern Louisiana    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Total oil and gas properties not subject to amortization, total 536  
Bakken    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Total oil and gas properties not subject to amortization, total 98  
Other    
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]    
Total oil and gas properties not subject to amortization, total $ 368