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 3 Months Ended 6 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
Jun. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Dec. 31, 2016
USD ($)
Business Acquisition [Line Items]                    
Proceeds from sales of oil and gas properties                 $ 250  
Gain from sale of property               $ 300 $ 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 $ 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