Quarterly report pursuant to Section 13 or 15(d)

Commitments And Contingencies (Narrative) (Details)

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Commitments And Contingencies (Narrative) (Details)
$ in Thousands
 1 Months Ended 9 Months Ended
Apr. 30, 2018
USD ($)
Sep. 30, 2018
USD ($)
item
Sep. 25, 2018
USD ($)
Dec. 31, 2017
USD ($)
Commitments And Contingencies [Line Items]        
Number of drilled wells required by agreement | item   2    
Number of appraisal wells required by agreement | item   2    
Estimated costs of wells, gross amount   $ 61,200    
Estimated costs of wells   20,500    
Estimated costs of technical studies   1,300    
Estimated costs of technical studies, net   400    
Abandonment Funding   10,808   $ 10,808
Abandonment cost related to annual funding   61,100    
Abandonment cost related to annual funding, net   19,000    
Accrued liabilities and other   17,662   12,991
Potential Fees From Customs Audits [Member]        
Commitments And Contingencies [Line Items]        
Accrued liabilities and other   1,300   1,300
Gabon [Member]        
Commitments And Contingencies [Line Items]        
Accrued liabilities, end of drilling activities, gross amount   5,000    
Accrued liabilities, end of drilling activities   1,700    
Abandonment Funding   10,800    
Contractual obligation     $ 21,800  
Abandonment funding, gross   $ 34,800    
Accrued estimated settlement       500
Tax examination settlement payment $ 200      
Tax penalties $ 200      
Offshore Gabon [Member]        
Commitments And Contingencies [Line Items]        
Production License Agreement Term Extended By Government   5 years    
Percentage of annual funding over seven years   12.14%    
Funding period for initial rate   7 years    
Second funding period of production license   3 years    
Percentage of annual funding over last three years   5.00%    
Funding period abandonment funding   10 years    
Number of contract extension periods | item   2    
FPSO Charter [Member]        
Commitments And Contingencies [Line Items]        
Number of extensions | item   2    
Period of charter (in years)   1 year    
Percentage of share in charter payment   31.10%    
Share in charter payment, approximate annual amount   $ 9,700    
Liabilities, guarantees' fair value   400   500
Contractual obligation   $ 61,800   $ 85,200