Quarterly report pursuant to Section 13 or 15(d)

Organization and Accounting Policies (Narrative) (Details)

v3.21.2
Organization and Accounting Policies (Narrative) (Details)
 3 Months Ended 9 Months Ended 24 Months Ended
Jun. 20, 2026
Feb. 25, 2021
Sep. 30, 2021
USD ($)
/ $
Sep. 30, 2020
USD ($)
Sep. 30, 2021
USD ($)
/ $
Sep. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
/ $
Feb. 24, 2021
Organization And Accounting Policies [Line Items]                
Impairment of proved crude oil and natural gas properties     $ 0 $ 0 $ 0 $ 30,625,000    
Receivable balance, gross, noncurrent     $ 9,600,000   $ 9,600,000   $ 4,500,000  
Abandonment funding payments missed             $ 2,900,000  
Exchange rate | / $     566.0   566.0   534.8  
Transfers between levels         $ 0 $ 0    
Office and Miscellaneous Equipment [Member]                
Organization And Accounting Policies [Line Items]                
Estimated useful life of assets         5 years      
Leasehold Improvements [Member] | Minimum [Member]                
Organization And Accounting Policies [Line Items]                
Estimated useful life of assets         5 years      
Leasehold Improvements [Member] | Maximum [Member]                
Organization And Accounting Policies [Line Items]                
Estimated useful life of assets         7 years      
Consortium [Member]                
Organization And Accounting Policies [Line Items]                
Receivable balance, gross, noncurrent     $ 14,400,000   $ 14,400,000   $ 13,400,000  
Prior Production Sharing Contract, Through September 17, 2018 [Member] | Government Of Gabon [Member]                
Organization And Accounting Policies [Line Items]                
Monthly royalty rate, based on production at the published price         13.00%      
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Government Of Gabon [Member]                
Organization And Accounting Policies [Line Items]                
Monthly royalty rate, based on production at the published price         13.00%      
Etame Marine Block [Member]                
Organization And Accounting Policies [Line Items]                
Impairment of proved crude oil and natural gas properties       $ 30,600,000        
Working interest ownership, percentage   58.80%           31.10%
Etame Marine Block [Member] | Sasol Gabon S.A. [Member]                
Organization And Accounting Policies [Line Items]                
Increase (decrease) in working interest ownership percentage   27.80%            
Etame Marine Block [Member] | Prior Production Sharing Contract, Through September 17, 2018 [Member] | Consortium [Member]                
Organization And Accounting Policies [Line Items]                
Working interest ownership, percentage     7.50%   7.50%      
Etame Marine Block [Member] | Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Government Of Gabon [Member]                
Organization And Accounting Policies [Line Items]                
Working interest ownership, percentage     7.50%   7.50%      
Etame Marine Block [Member] | Scenario, Forecast [Member] | Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member]                
Organization And Accounting Policies [Line Items]                
Increase (decrease) in working interest ownership percentage (1.60%)              
Etame Marine Block [Member] | Scenario, Forecast [Member] | Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Government Of Gabon [Member]                
Organization And Accounting Policies [Line Items]                
Increase (decrease) in working interest ownership percentage 2.50%              
Working interest ownership, percentage 10.00%