Quarterly report pursuant to Section 13 or 15(d)

Acquisitions And Dispositions (Narrative) (Details)

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Acquisitions And Dispositions (Narrative) (Details)
$ in Thousands, a in Millions
 1 Months Ended 9 Months Ended
Nov. 22, 2016
Mar. 14, 2016
USD ($)
Jan. 01, 2014
Apr. 30, 2017
USD ($)
Oct. 31, 2014
item
Apr. 30, 2014
USD ($)
Nov. 30, 2006
USD ($)
a
item
Sep. 30, 2017
USD ($)
Dec. 31, 2016
USD ($)
Business Acquisition [Line Items]                  
Proceeds from sales of oil and gas properties               $ 250  
Gain from sale of property               $ 300  
Offshore Gabon [Member]                  
Business Acquisition [Line Items]                  
Production license agreement term extended by government               5 years  
East Poplar Dome Field [Member]                  
Business Acquisition [Line Items]                  
Proceeds from sales of oil and gas properties       $ 300          
Joint Operating With Republic Of Angola [Member]                  
Business Acquisition [Line Items]                  
Production license agreement term             4 years    
Production license agreement term extended by government             3 years    
Area under acquire property exploration rights agreement term (acres) | a             1.4    
Number of exploration wells | item             2    
Number Of Additional Exploration Wells | item         2        
Joint operation agreement related to third party in working interest percentage             40.00%    
Additional joint operation agreement related to third party in working interest percentage             10.00%    
Stipulated payment for each exploration well, under PSA terms             $ 10,000    
Drilling commitment, net             $ 5,000    
Liability for the penalty               $ 15,000 $ 15,000
Write off of bad debt           $ 7,600      
Working interest ownership other, percentage     40.00%            
Etame [Member]                  
Business Acquisition [Line Items]                  
Percentage of working interest 2.98%                
Percentage of participating interest 3.23%                
Effective date of acquisition               Aug. 01, 2016  
Sonangol P&P [Member]                  
Business Acquisition [Line Items]                  
Payment from joint venture partners   $ 19,000              
Write off of bad debt   7,600              
Interest income   $ 3,200