Quarterly report pursuant to Section 13 or 15(d)

Acquisitions (Fair Value of Net Assets Acquired ) (Details)

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Acquisitions (Fair Value of Net Assets Acquired ) (Details) - Delaware Basin
$ in Thousands
Feb. 13, 2017
USD ($)
Business Acquisition [Line Items]  
Asset retirement obligations $ (168)
Net assets acquired 632,947
Evaluated oil and natural gas properties  
Business Acquisition [Line Items]  
Oil and natural gas properties 134,315
Unevaluated oil and natural gas properties  
Business Acquisition [Line Items]  
Oil and natural gas properties $ 498,800