Annual report pursuant to Section 13 and 15(d)

Income Taxes (Narrative) (Details)

v3.20.1
Income Taxes (Narrative) (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2019
USD ($)
item
Dec. 31, 2018
USD ($)
Dec. 31, 2017
Income Taxes [Line Items]      
Deferred tax assets $ 108,787 $ 131,012  
Valuation allowance $ 84,628 $ 90,935  
Statutory tax rate 21.00% 21.00% 35.00%
Expired foreign tax credits $ 9,600    
Interest or penalties accrued $ 0 $ 0  
Production license agreement term extended by government 5 years    
Deferred tax assets $ 24,159 $ 40,077  
Prior Production Sharing Contract, Through September 17, 2018 [Member]      
Income Taxes [Line Items]      
Entitled percent for consortium after initial royalty percentage 70.00%    
Production Sharing Contract, September 17, 2018 Through September 16, 2028 [Member]      
Income Taxes [Line Items]      
Entitled percent for consortium after initial royalty percentage 80.00%    
Production Sharing Contract, After September 16, 2028 [Member]      
Income Taxes [Line Items]      
Entitled percent for consortium after initial royalty percentage 70.00%    
United Kingdom Tax Authority [Member]      
Income Taxes [Line Items]      
Deferred tax assets $ 8,700    
Gabon Tax Authority [Member]      
Income Taxes [Line Items]      
Deferred tax assets $ 15,900    
Minimum [Member]      
Income Taxes [Line Items]      
Allocation of remaining profit production, government payments, percentage 50.00%    
Number of contract extension periods | item 2    
Minimum [Member] | Domestic Tax Authority [Member]      
Income Taxes [Line Items]      
Foreign tax credit carryforward, expiration dates Dec. 31, 2035    
Minimum [Member] | Foreign Tax Authority [Member]      
Income Taxes [Line Items]      
Foreign tax credit carryforward, expiration dates Dec. 31, 2020    
Maximum [Member]      
Income Taxes [Line Items]      
Allocation of remaining profit production, government payments, percentage 60.00%    
Maximum [Member] | Domestic Tax Authority [Member]      
Income Taxes [Line Items]      
Foreign tax credit carryforward, expiration dates Dec. 31, 2037    
Maximum [Member] | Foreign Tax Authority [Member]      
Income Taxes [Line Items]      
Foreign tax credit carryforward, expiration dates Dec. 31, 2025