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 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Dec. 31, 2015
Segment Reporting Information [Line Items]          
Revenues-oil and natural gas sales $ 18,847 $ 27,137 $ 29,823 $ 45,376  
Depreciation, depletion and amortization 1,945 9,299 4,186 15,234  
Impairment of proved properties   5,821   11,220  
Bad debt expense (recovery) and other 171 296 (7,115) 576  
Other operating expense 754   9,635    
Operating income (loss) 4,573 (1,030) (2,075) (36,308)  
Interest income (expense), net (1,470) (339) 1,243 (645)  
Income tax expense 3,001 4,273 7,653 7,638  
Additions to properties and equipment (2,353) 18,885 (2,353) 31,581  
Long lived assets 27,080   27,080   $ 33,373
Total assets 91,657   91,657   123,958
Gabon [Member]          
Segment Reporting Information [Line Items]          
Revenues-oil and natural gas sales     29,672 45,091  
Depreciation, depletion and amortization     3,976 14,784  
Impairment of proved properties       11,220  
Bad debt expense (recovery) and other     514    
Other operating expense     9,635    
Operating income (loss)     (3,532) (2,279)  
Interest income (expense), net     (1,956) (650)  
Income tax expense     4,579 7,638  
Additions to properties and equipment     (2,493) 33,419  
Angola [Member]          
Segment Reporting Information [Line Items]          
Depreciation, depletion and amortization     6 6  
Bad debt expense (recovery) and other     (7,629)    
Operating income (loss)     7,007 (28,844)  
Interest income (expense), net     3,201    
Income tax expense     3,074    
Additions to properties and equipment       (1,973)  
Equatorial Guinea [Member]          
Segment Reporting Information [Line Items]          
Operating income (loss)     (135) (657)  
United States [Member]          
Segment Reporting Information [Line Items]          
Revenues-oil and natural gas sales     151 285  
Depreciation, depletion and amortization     63 327  
Bad debt expense (recovery) and other       576  
Operating income (loss)     (3) (414)  
Additions to properties and equipment     140 (16)  
Corporate And Other [Member]          
Segment Reporting Information [Line Items]          
Depreciation, depletion and amortization     141 117  
Operating income (loss)     (5,412) (4,114)  
Interest income (expense), net     (2) 5  
Additions to properties and equipment       $ 151  
Operating Segments [Member] | Gabon [Member]          
Segment Reporting Information [Line Items]          
Revenues-oil and natural gas sales 18,764 26,991      
Depreciation, depletion and amortization 1,833 9,078      
Impairment of proved properties   5,821      
Bad debt expense (recovery) and other 171        
Other operating expense 754        
Operating income (loss) 8,424 2,266      
Interest income (expense), net (1,468) (343)      
Income tax expense 2,894 4,273      
Additions to properties and equipment (2,493) 17,680      
Total assets 75,259   75,259   98,858
Operating Segments [Member] | Angola [Member]          
Segment Reporting Information [Line Items]          
Depreciation, depletion and amortization 3 3      
Operating income (loss) (299) (978)      
Income tax expense 107        
Additions to properties and equipment   1,135      
Total assets 2,290   2,290   10,304
Operating Segments [Member] | Equatorial Guinea [Member]          
Segment Reporting Information [Line Items]          
Operating income (loss) (87) (418)      
Total assets 10,174   10,174   10,200
Operating Segments [Member] | United States [Member]          
Segment Reporting Information [Line Items]          
Revenues-oil and natural gas sales 83 146      
Depreciation, depletion and amortization 42 157      
Bad debt expense (recovery) and other   296      
Operating income (loss)   (663)      
Additions to properties and equipment 140 (16)      
Total assets 1,314   1,314   1,470
Corporate And Other [Member]          
Segment Reporting Information [Line Items]          
Depreciation, depletion and amortization 67 61      
Operating income (loss) (3,465) (1,237)      
Interest income (expense), net (2) 4      
Additions to properties and equipment   $ 86      
Corporate And Other [Member] | Corporate And Other [Member]          
Segment Reporting Information [Line Items]          
Total assets $ 2,620   $ 2,620   $ 3,126