Quarterly report pursuant to Section 13 or 15(d)

Segment Information (Segment Activity) (Detail)

v3.5.0.2
Segment Information (Segment Activity) (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Mar. 31, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Segment Reporting Information [Line Items]            
Revenues-oil and natural gas sales $ 14,635 $ 11,000 $ 17,546 $ 44,458 $ 62,922  
Depreciation, depletion and amortization 1,607   8,256 5,787 23,484  
Impairment of proved properties 88   17,988 88 29,208  
Bad debt expense and other 63   2,750 577 3,326  
Other operating expense 324     9,959    
Operating income (loss) 2,858   (30,951) (6,224) (38,415)  
Interest income (expense), net (327)   (462) (2,285) (1,107)  
Income tax expense 2,198   2,707 6,884 10,345  
Additions to properties and equipment 681   10,804 (1,672) 44,357  
Total assets 78,202     78,202   $ 123,958
Continuing Operations [Member]            
Segment Reporting Information [Line Items]            
Total assets 76,455     76,455   115,573
Operating Segments [Member] | Gabon [Member]            
Segment Reporting Information [Line Items]            
Revenues-oil and natural gas sales 14,540   17,405 44,212 62,496  
Depreciation, depletion and amortization 1,508   8,060 5,484 22,844  
Impairment of proved properties     17,988   29,208  
Bad debt expense and other 63   2,750 577 3,326  
Other operating expense 324     9,959    
Operating income (loss) 5,013   (29,007) 1,481 (31,286)  
Interest income (expense), net (329)   (294) (2,285) (944)  
Income tax expense 2,305   2,707 6,884 10,345  
Additions to properties and equipment 674   10,796 (1,819) 44,215  
Operating Segments [Member] | Gabon [Member] | Continuing Operations [Member]            
Segment Reporting Information [Line Items]            
Total assets 55,833     55,833   98,858
Operating Segments [Member] | Equatorial Guinea [Member]            
Segment Reporting Information [Line Items]            
Operating income (loss) (184)   (287) (319) (944)  
Operating Segments [Member] | Equatorial Guinea [Member] | Continuing Operations [Member]            
Segment Reporting Information [Line Items]            
Total assets 10,169     10,169   10,200
Operating Segments [Member] | United States [Member]            
Segment Reporting Information [Line Items]            
Revenues-oil and natural gas sales 95   141 246 426  
Depreciation, depletion and amortization 38   140 121 467  
Impairment of proved properties 88     88    
Operating income (loss) (61)   42 (64) (372)  
Additions to properties and equipment     1 140 (16)  
Operating Segments [Member] | United States [Member] | Continuing Operations [Member]            
Segment Reporting Information [Line Items]            
Total assets 1,379     1,379   1,470
Corporate And Other [Member]            
Segment Reporting Information [Line Items]            
Depreciation, depletion and amortization 61   56 182 173  
Operating income (loss) (1,910)   (1,699) (7,322) (5,813)  
Interest income (expense), net 2   (168)   (163)  
Income tax expense (107)          
Additions to properties and equipment 7   $ 7 7 $ 158  
Corporate And Other [Member] | Continuing Operations [Member]            
Segment Reporting Information [Line Items]            
Total assets $ 9,074     $ 9,074   $ 5,045