Quarterly report pursuant to Section 13 or 15(d)

Acquisitions (Narrative) (Details)

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Acquisitions (Narrative) (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended
Feb. 13, 2017
USD ($)
a
Oct. 20, 2016
USD ($)
a
May 26, 2016
USD ($)
a
$ / shares
shares
Apr. 30, 2017
USD ($)
a
Dec. 31, 2016
USD ($)
Business Acquisition [Line Items]          
Acquisition deposit | $         $ 46,138
Midland Basin in Howard County, Texas [Member] | October 20, 2016 Acquisitions [Member] | Plymouth Transaction [Member]          
Business Acquisition [Line Items]          
Consideration transferred | $   $ 339,687      
Gas and oil area, developed and undeveloped, gross   6,904      
Gas and oil area, developed and undeveloped, net   5,952      
Working interest   82.00%      
Net revenue interest   62.00%      
Midland Basin in Howard County, Texas [Member] | May 26, 2016 Acquisitions [Member] | Big Star Transaction [Member]          
Business Acquisition [Line Items]          
Consideration transferred | $     $ 220,000    
Aggregate purchase price | $     $ 329,573    
Shares of common stock issued in acquisition | shares     9,333,333    
Sales price of common stock | $ / shares     $ 11.74    
Gas and oil area, developed and undeveloped, gross     17,298    
Gas and oil area, developed and undeveloped, net     14,089    
Working interest     81.00%    
Net revenue interest     61.00%    
Delaware Basin [Member] | February 13, 2017 Acquisitions [Member] | Ameredev Transaction [Member]          
Business Acquisition [Line Items]          
Consideration transferred | $ $ 632,947        
Aggregate purchase price | $ $ 632,947        
Gas and oil area, developed and undeveloped, gross 29,175        
Gas and oil area, developed and undeveloped, net 16,688        
Working interest 82.00%        
Delaware Basin [Member] | April 2017 Acquisitions [Member] | Subsequent Event [Member]          
Business Acquisition [Line Items]          
Consideration transferred | $       $ 52,500  
Gas and oil area, developed and undeveloped, gross       7,031  
Gas and oil area, developed and undeveloped, net       2,488