Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies (Narrative) (Details)

v3.22.0.1
Summary of Significant Accounting Policies (Narrative) (Details)
$ in Millions
 12 Months Ended
Jun. 20, 2026
Feb. 25, 2021
Dec. 31, 2021
USD ($)
contract
/ $
Dec. 31, 2020
USD ($)
/ $
Dec. 31, 2019
USD ($)
Feb. 24, 2021
Organization And Accounting Policies [Line Items]            
Receivable balance, gross, noncurrent     $ 9.6      
Exchange rate | / $     578.2 534.8    
Number of contracts entered into | contract     2      
Gain (loss) on foreign currency transaction     $ (0.7) $ 0.2 $ (0.2)  
Sasol Gabon S.A. [Member]            
Organization And Accounting Policies [Line Items]            
Abandonment funding payment due     4.3      
Consortium [Member]            
Organization And Accounting Policies [Line Items]            
Receivable balance, gross, noncurrent     $ 14.5      
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]            
Organization And Accounting Policies [Line Items]            
Other receivables     $ 10.0      
Other accounts payable     5.4      
Other accrued liabilities     $ 4.6      
Etame Marine Block [Member] | Sasol Gabon S.A. [Member]            
Organization And Accounting Policies [Line Items]            
Increase (decrease) in working interest ownership percentage   27.80%        
Working interest ownership, percentage   58.80%       31.10%
Etame Marine Block [Member] | Government Of Gabon [Member]            
Organization And Accounting Policies [Line Items]            
Monthly royalty rate, based on production at the published price     13.00%      
Working interest ownership, percentage     7.50%      
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%      
Etame Marine Block [Member] | Scenario, Forecast [Member] | Government Of Gabon [Member]            
Organization And Accounting Policies [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]            
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%