Quarterly report pursuant to Section 13 or 15(d)

Acquisitions (Narrative) (Details)

v3.10.0.1
Acquisitions (Narrative) (Details)
 3 Months Ended
May 23, 2018
USD ($)
a
Jun. 05, 2017
USD ($)
a
Feb. 13, 2017
USD ($)
a
Mar. 31, 2018
USD ($)
Jun. 30, 2018
USD ($)
Dec. 31, 2017
USD ($)
May 19, 2017
USD ($)
Dec. 31, 2016
USD ($)
Business Acquisition [Line Items]                
Acquisition deposit         $ 28,500,000 $ 900,000    
6.125% senior unsecured notes due 2024                
Business Acquisition [Line Items]                
Debt instrument aggregate principal amount             $ 200,000,000  
Debt instrument, interest rate, stated (as a percent)         6.125%   6.125%  
Cimarex Energy Company                
Business Acquisition [Line Items]                
Gas and oil area, developed and undeveloped, gross (in acres) | a 47,538              
Gas and oil area, developed and undeveloped, net (in acres) | a 28,657              
Consideration transferred $ 570,000,000              
Acquisition deposit $ 28,500,000              
Monarch and Wildhorse                
Business Acquisition [Line Items]                
Consideration transferred       $ 35,900,000        
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%          
Net revenue interest (as a percent)     75.00%          
Acquisition deposit               $ 46,138,000