Annual report pursuant to Section 13 and 15(d)

Summary Of Significant Accounting Policies (Narrative) (Details)

v3.8.0.1
Summary Of Significant Accounting Policies (Narrative) (Details)
$ in Thousands, XAF in Billions
 12 Months Ended
Dec. 31, 2017
USD ($)
item
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2017
XAF
XAF / $
Dec. 31, 2017
USD ($)
XAF / $
Dec. 31, 2016
XAF
Dec. 31, 2016
USD ($)
Organization And Accounting Policies [Line Items]              
Exchange rate | XAF / $       547.500 547.500    
Recorded allowance $ 452 $ 1,222 $ 2,699        
Other operating income (expense), net $ (84) (266) (1,092)        
Receivable balance, net         $ 3,556   $ 6,751
Value added tax reimbursement monthly payment     300        
Value added tax and other receivables, net of allowance of $6.5 million and $4.7 million at December 31, 2017 and December 31, 2016, respectively         6,925   5,110
Number of VAT reimbursement payments | item 36            
Gas imbalance receivable         0   0
Gains (Loss) on foreign currency transactions $ 500 30 800        
Interest expense capitalized 0 0 800        
Settlement of derivatives 200            
Scenario, Adjustment [Member]              
Organization And Accounting Policies [Line Items]              
Accrued liabilities         (2,600)    
Gabon [Member]              
Organization And Accounting Policies [Line Items]              
Recorded allowance 452 1,222 2,699        
Receivable balance, gross | XAF       XAF 21.2   XAF 16.3  
Receivable balance, net | XAF       XAF 7.1   XAF 4.9  
Value added tax and other receivables, net of allowance of $6.5 million and $4.7 million at December 31, 2017 and December 31, 2016, respectively     2,700   $ 400   $ 700
Gabon And Angola [Member]              
Organization And Accounting Policies [Line Items]              
Other operating income (expense), net $ 300 $ (300) $ (1,500)        
Office And Miscellaneoud Equipment [Member]              
Organization And Accounting Policies [Line Items]              
Estimated useful life 5 years            
Leasehold Improvements [Member] | Minimum [Member]              
Organization And Accounting Policies [Line Items]              
Estimated useful life 5 years            
Leasehold Improvements [Member] | Maximum [Member]              
Organization And Accounting Policies [Line Items]              
Estimated useful life 7 years