Annual report pursuant to Section 13 and 15(d)

Revenue (Narrative) (Details)

v3.20.4
Revenue (Narrative) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Jun. 20, 2026
Dec. 31, 2019
Dec. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Interval period, between lifting 1 month      
Purchase agreement payment period 30 days      
Foreign taxes payable attributable to sharing obligation $ 0.9   $ 5.7  
Minimum [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Lifting period, time to complete 1 day      
Maximum [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Lifting period, time to complete 2 days      
Prior Production Sharing Contract, Through September 17, 2018 [Member] | Government Of Gabon [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [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] | Consortium [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Monthly royalty rate, based on production at the published price 13.00%      
Etame Marine Block [Member] | Government Of Gabon [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Working interest ownership, percentage 7.50%      
Monthly royalty rate, based on production at the published price 13.00%      
Etame Marine Block [Member] | Prior Production Sharing Contract, Through September 17, 2018 [Member] | Consortium [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Working interest ownership, percentage 7.50%      
Etame Marine Block [Member] | Prior Production Sharing Contract, Through September 17, 2018 [Member] | Government Of Gabon [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Working interest ownership, percentage       7.50%
Etame Marine Block [Member] | Scenario, Forecast [Member] | Government Of Gabon [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Working interest ownership, percentage   10.00%    
Etame Marine Block [Member] | Scenario, Forecast [Member] | Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member] | Government Of Gabon [Member]        
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]        
Working interest ownership, percentage   10.00%