Quarterly report pursuant to Section 13 or 15(d)

Organization and Accounting Policies (Narrative) (Details)

v3.19.2
Organization and Accounting Policies (Narrative) (Details)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2019
USD ($)
/ $
Jun. 30, 2018
USD ($)
Jun. 30, 2019
USD ($)
/ $
Jun. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
/ $
Organization And Accounting Policies [Line Items]          
Receivable balance, net $ 13,828   $ 13,828   $ 11,907
Exchange rate | / $         573.0
Bad debt recovery (expense) (5) $ (145) 24 $ (89)  
Transfers between levels 0   $ 0    
Monthly royalty rate, based on production at the published price     13.00%    
Working interest of carried partner, percentage     7.50%    
Future working interest of carried partner percentage     10.00%    
Loss on foreign currency transactions (0) 200 $ 200 100  
Gabon          
Organization And Accounting Policies [Line Items]          
Receivable balance, gross, noncurrent 8,000   8,000    
Receivable balance, net, noncurrent $ 2,700   $ 2,700    
Exchange rate | / $ 576.6   576.6    
Bad debt recovery (expense) $ (3) $ 100 $ 29 $ 100