Annual report pursuant to Section 13 and 15(d)

Segment Information (Segment Activity) (Details)

v3.8.0.1
Segment Information (Segment Activity) (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Segment Reporting Information [Line Items]                      
Revenues-oil and natural gas sales $ 17,156 $ 18,178 $ 20,425 $ 21,266 $ 15,326 $ 14,635 $ 18,847 $ 10,976 $ 77,025 $ 59,784 $ 80,445
Depreciation, depletion and amortization                 6,457 6,926 32,998
Impairment of proved properties                   88 81,322
Bad debt expense and other                 452 1,222 2,968
Other operating expense                   8,853  
Operating income (loss) 2,495 $ 3,721 $ 5,587 $ 8,148 819 $ 3,690 $ 4,615 $ (13,515) 19,951 (4,391) (103,106)
Other, net                 2,113 (2,015) (1,536)
Interest expense, net                 (1,414) (2,613) (1,325)
Income tax expense                 10,378 9,248 14,587
Additions to properties and equipment - accrual                 1,702 (4,061) 66,419
Total assets 79,633       81,032       79,633 81,032  
Continuing Operations [Member]                      
Segment Reporting Information [Line Items]                      
Total assets 23,221       28,019       23,221 28,019  
Operating Segments [Member] | Gabon Segment [Member]                      
Segment Reporting Information [Line Items]                      
Revenues-oil and natural gas sales                 76,978 59,460 79,947
Depreciation, depletion and amortization                 6,196 6,531 32,125
Impairment of proved properties                     78,080
Bad debt expense and other                 452 1,222 2,968
Other operating expense                   8,853  
Operating income (loss)                 28,488 3,901 (87,243)
Other, net                 3,142 (22) (1,034)
Interest expense, net                 (1,414) (2,614) (1,144)
Income tax expense                 11,638 9,248 13,238
Additions to properties and equipment - accrual                 1,576 (4,242) 66,269
Operating Segments [Member] | Equatorial Guinea Segment [Member]                      
Segment Reporting Information [Line Items]                      
Operating income (loss)                 (122) (384) (1,342)
Other, net                 15 (8) (33)
Operating Segments [Member] | U. S. Segment [Member]                      
Segment Reporting Information [Line Items]                      
Revenues-oil and natural gas sales                 47 324 498
Depreciation, depletion and amortization                 1 151 633
Impairment of proved properties                   88 3,242
Operating income (loss)                 352 (72) (4,366)
Operating Segments [Member] | Continuing Operations [Member] | Gabon Segment [Member]                      
Segment Reporting Information [Line Items]                      
Total assets 12,638       17,291       12,638 17,291  
Operating Segments [Member] | Continuing Operations [Member] | Equatorial Guinea Segment [Member]                      
Segment Reporting Information [Line Items]                      
Total assets 10,000       10,000       10,000 10,000  
Corporate And Other [Member]                      
Segment Reporting Information [Line Items]                      
Depreciation, depletion and amortization                 260 244 240
Operating income (loss)                 (8,767) (7,836) (10,155)
Other, net                 (1,044) (1,985) (469)
Interest expense, net                   1 (181)
Income tax expense                 (1,260)   1,349
Additions to properties and equipment - accrual                 126 181 $ 150
Corporate And Other [Member] | Continuing Operations [Member]                      
Segment Reporting Information [Line Items]                      
Total assets $ 583       $ 728       $ 583 $ 728