Quarterly report pursuant to Section 13 or 15(d)

Dispositions (Narrative) (Details)

v3.19.2
Dispositions (Narrative) (Details) - USD ($)
$ in Thousands
1 Months Ended 3 Months Ended 6 Months Ended
Jul. 31, 2019
Nov. 30, 2006
Jun. 30, 2019
Mar. 31, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Business Acquisition [Line Items]                
Income (loss) from discontinued operations, net of tax     $ (162)   $ (343) $ 5,509 $ (395)  
Discontinued Operations [Member] | Joint Operating With Republic Of Angola [Member]                
Business Acquisition [Line Items]                
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 potential payment       $ 4,500       $ 15,000
Write off of receivable       3,300        
Income (loss) from discontinued operations, net of tax     $ (162) $ 5,700 $ (343) $ 5,509 $ (395)  
Discontinued Operations [Member] | Joint Operating With Republic Of Angola [Member] | Subsequent Event                
Business Acquisition [Line Items]                
Payment for settlement $ 4,500