Quarterly report pursuant to Section 13 or 15(d)

Acquisitions (Narrative) (Details)

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Acquisitions (Narrative) (Details)
Jun. 05, 2017
USD ($)
a
Feb. 13, 2017
USD ($)
a
Oct. 20, 2016
USD ($)
a
May 26, 2016
USD ($)
a
$ / shares
shares
Sep. 30, 2017
USD ($)
May 19, 2017
USD ($)
Dec. 31, 2016
USD ($)
Oct. 03, 2016
USD ($)
Business Acquisition [Line Items]                
Acquisition deposit         $ 0   $ 46,138,000  
6.125% senior unsecured notes due 2024                
Business Acquisition [Line Items]                
Debt instrument aggregate principal amount           $ 200,000,000   $ 400,000,000
Debt instrument, interest rate, stated (as a percent)         6.125% 6.125%   6.125%
Delaware Basin                
Business Acquisition [Line Items]                
Gas and oil area, developed and undeveloped, gross (in acres) | a 7,031 29,175            
Gas and oil area, developed and undeveloped, net (in acres) | a 2,488 16,688            
Consideration transferred $ 52,500,000 $ 646,559,000            
Working interest (as a percent)   82.00%            
Acquisition deposit             $ 46,138,000  
Aggregate purchase price   $ 646,559,000            
Midland Basin in Howard County, Texas                
Business Acquisition [Line Items]                
Gas and oil area, developed and undeveloped, gross (in acres) | a     6,904 17,298        
Gas and oil area, developed and undeveloped, net (in acres) | a     5,952 14,089        
Consideration transferred     $ 339,687,000 $ 220,000,000        
Working interest (as a percent)     82.00% 81.00%        
Net revenue interest (as a percent)     62.00% 61.00%        
Shares of common stock issued in acquisition (in shares) | shares       9,333,333        
Sales price of common stock (in dollars per share) | $ / shares       $ 11.74        
Aggregate purchase price       $ 329,573,000