Quarterly report pursuant to Section 13 or 15(d)

Segment Information (Segment Activity) (Details)

v3.8.0.1
Segment Information (Segment Activity) (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Segment Reporting Information [Line Items]      
Revenues-oil and natural gas sales $ 27,645 $ 21,266  
Depreciation, depletion and amortization 1,124 1,869  
Bad debt expense (recovery) and other (56) 98  
Operating income (loss) 13,038 8,148  
Other, net 69 (116)  
Interest expense, net 354 403  
Income tax expense 4,042 3,194  
Additions to properties and equipment - accrual 427 262  
Total assets 92,185   $ 79,633
Continuing Operations [Member]      
Segment Reporting Information [Line Items]      
Long lived assets 22,599   23,221
Total assets 89,155   76,797
Operating Segments [Member] | Gabon Segment [Member]      
Segment Reporting Information [Line Items]      
Revenues-oil and natural gas sales 27,643 21,246  
Depreciation, depletion and amortization 1,059 1,809  
Bad debt expense (recovery) and other (56) 98  
Operating income (loss) 15,697 10,960  
Other, net 69    
Interest expense, net 354 403  
Income tax expense 4,042 3,194  
Additions to properties and equipment - accrual 428 262  
Operating Segments [Member] | Equatorial Guinea Segment [Member]      
Segment Reporting Information [Line Items]      
Operating income (loss) (30) (38)  
Other, net 3    
Operating Segments [Member] | Continuing Operations [Member] | Gabon Segment [Member]      
Segment Reporting Information [Line Items]      
Long lived assets 12,081   12,638
Total assets 75,718   63,122
Operating Segments [Member] | Continuing Operations [Member] | Equatorial Guinea Segment [Member]      
Segment Reporting Information [Line Items]      
Long lived assets 10,000   10,000
Total assets 10,097   10,095
Corporate And Other [Member]      
Segment Reporting Information [Line Items]      
Revenues-oil and natural gas sales 2 20  
Depreciation, depletion and amortization 65 60  
Operating income (loss) (2,629) $ (2,774)  
Other, net (3)    
Additions to properties and equipment - accrual (1)    
Corporate And Other [Member] | Continuing Operations [Member]      
Segment Reporting Information [Line Items]      
Long lived assets 518   583
Total assets $ 3,340   $ 3,580