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 6 Months Ended
Apr. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
item
Dec. 31, 2017
USD ($)
Commitments And Contingencies [Line Items]      
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   16,893 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]      
Abandonment Funding   10,800  
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   $ 69,700 $ 85,200