Quarterly report pursuant to Section 13 or 15(d)

JV Drilling Program - Additional Information (Details)

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JV Drilling Program - Additional Information (Details)
 1 Months Ended 3 Months Ended
Apr. 27, 2018
USD ($)
Mar. 12, 2018
DrillingProject
May 03, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Oil And Gas In Process Activities [Line Items]            
Prepaid assets       $ 20,197,000 $ 13,419,000 $ 20,197,000
Oil and natural gas properties       573,352,000 579,016,000  
Other assets       64,414,000 60,393,000  
Accounts payable       77,444,000 $ 83,665,000  
Monza Energy LLC            
Oil And Gas In Process Activities [Line Items]            
Prepaid assets       2,400,000    
Oil and natural gas properties       44,900,000    
Other assets       2,400,000    
Accounts payable       1,000,000    
Maximum exposure amount by related party       48,700,000    
Maximum exposure amount, cash contribution       6,700,000    
Maximum exposure amount, fair value for conveyance of working interest       42,000,000    
JV Drilling Program            
Oil And Gas In Process Activities [Line Items]            
Capital expenditures reimbursement, net       $ 20,000,000    
JV Drilling Program | Mr. Tracy W. Krohn            
Oil And Gas In Process Activities [Line Items]            
Minority interest ownership percentage by joint venture       4.50%    
JV Drilling Program | Subsequent Event            
Oil And Gas In Process Activities [Line Items]            
Commitment amount by investors     $ 297,600,000      
JV Drilling Program | Monza Energy LLC            
Oil And Gas In Process Activities [Line Items]            
Number of drilling projects | DrillingProject   14        
Joint maturity period   3 years        
Joint venture ownership percentage contributed to related party   88.94%        
Joint venture ownership percentage   11.06%        
Projected cost to fully develop projects excluding contingencies       $ 298,600,000    
Projected cost to fully develop projects with contingent costs       373,000,000    
Indirect cash commitment through Monza       37,500,000    
Percentage of revenue from joint venture   30.00%        
Percentage of estimated well cost   20.00%        
JV Drilling Program | Monza Energy LLC | Mr. Tracy W. Krohn            
Oil And Gas In Process Activities [Line Items]            
Capital commitment       13,400,000    
Maximum capital commitment amount subject to joining of additional investors       $ 16,800,000    
JV Drilling Program | Monza Energy LLC | Subsequent Event            
Oil And Gas In Process Activities [Line Items]            
Commitment amount by investors $ 297,600,000