Quarterly report pursuant to Section 13 or 15(d)

Segment Information (Segment Activity) (Detail)

v3.4.0.3
Segment Information (Segment Activity) (Detail) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Dec. 31, 2015
Segment Reporting Information [Line Items]      
Revenues-oil and natural gas sales $ 10,976 $ 18,239  
Depreciation, depletion and amortization 2,241 5,935  
Impairment of proved properties   5,399  
Bad debt expense (recovery) and other (7,286) 280  
Operating income (loss) (6,648) (35,278)  
Interest income (expense), net 2,713 (306)  
Income tax expense 4,652 3,365  
Additions to properties and equipment   31,209  
Long lived assets 31,162   $ 33,373
Total assets 116,690   123,958
Operating Segments [Member] | Gabon [Member]      
Segment Reporting Information [Line Items]      
Revenues-oil and natural gas sales 10,908 18,100  
Depreciation, depletion and amortization 2,143 5,706  
Impairment of proved properties   5,399  
Bad debt expense (recovery) and other 343 280  
Operating income (loss) (11,956) (4,545)  
Interest income (expense), net (488) (307)  
Income tax expense 1,685 3,365  
Additions to properties and equipment   30,561  
Total assets 82,582   98,858
Operating Segments [Member] | Angola [Member]      
Segment Reporting Information [Line Items]      
Depreciation, depletion and amortization 3 3  
Bad debt expense (recovery) and other (7,629)    
Operating income (loss) 7,306 (27,866)  
Interest income (expense), net 3,201    
Income tax expense 2,967    
Additions to properties and equipment   583  
Total assets 20,789   10,304
Operating Segments [Member] | Equatorial Guinea [Member]      
Segment Reporting Information [Line Items]      
Operating income (loss) (48) (239)  
Total assets 10,186   10,200
Operating Segments [Member] | United States [Member]      
Segment Reporting Information [Line Items]      
Revenues-oil and natural gas sales 68 139  
Depreciation, depletion and amortization 21 170  
Operating income (loss) (3) 248  
Additions to properties and equipment   65  
Total assets 1,299   1,470
Corporate And Other [Member]      
Segment Reporting Information [Line Items]      
Depreciation, depletion and amortization 74 56  
Operating income (loss) (1,947) (2,876)  
Interest income (expense), net   $ 1  
Total assets $ 1,834   $ 3,126