Quarterly report pursuant to Section 13 or 15(d)

Oil And Natural Gas Properties And Equipment (Details)

v3.10.0.1
Oil And Natural Gas Properties And Equipment (Details)
$ in Thousands
 9 Months Ended
Sep. 26, 2018
USD ($)
Sep. 17, 2018
item
Sep. 30, 2018
USD ($)
item
Sep. 30, 2017
USD ($)
Sep. 25, 2018
USD ($)
Property Plant And Equipment [Line Items]          
Reduction in VAT receivable     $ 658 $ 2,783  
Allocated to proved leasehold cost     10,900    
Allocated to unproved leasehold cost     6,700    
VAT receivable, net of valuation allowance     $ 4,200    
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    
Entitled percent for consortium after initial royalty percentage     70.00%    
Monthly royalty rate, based on production at the published price     13.00%    
Future entitled percent for consortium after initial royalty percentage     80.00%    
Period of increased cost recovery percentage     10 years    
Additional increase to working interest ownership transferred from company, percent     0.80%    
Office And Miscellaneous Equipment [Member]          
Property Plant And Equipment [Line Items]          
Estimated useful life     5 years    
Leasehold Improvements [Member] | Maximum [Member]          
Property Plant And Equipment [Line Items]          
Estimated useful life     7 years    
Leasehold Improvements [Member] | Minimum [Member]          
Property Plant And Equipment [Line Items]          
Estimated useful life     5 years    
Etame Field [Member]          
Property Plant And Equipment [Line Items]          
Percent of participating interest     33.575%    
Number of exploitation areas | item   3      
Period of agreement for exploitation areas   10 years      
Number of contract extension periods | item   2      
Production license agreement term extended by government   5 years      
Gabon [Member]          
Property Plant And Equipment [Line Items]          
Contractual commitment, gross         $ 65,000
Contractual obligation         $ 21,800
Cash paid for signing bonus, gross amount $ 35,000        
Payment of signing bonus, allocated to proved and unproved property 11,800        
Reduction in VAT receivable, gross amount 25,000        
Reduction in VAT receivable $ 8,400        
Accrued liabilities, end of drilling activities, gross amount     $ 5,000    
Accrued liabilities, end of drilling activities     $ 1,700    
Gabon [Member] | Government Of Gabon [Member]          
Property Plant And Equipment [Line Items]          
Working interest ownership, percentage     7.50%    
Additional increase to working interest ownership, percent     2.50%