Annual report pursuant to Section 13 and 15(d)

Segment Information - Segment Activity (Detail)

v2.4.0.8
Segment Information - Segment Activity (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Segment Reporting Information [Line Items]                      
Revenues $ 58,282 $ 37,740 $ 29,118 $ 44,137 $ 53,553 $ 37,630 $ 58,818 $ 45,286 $ 169,277 $ 195,287 $ 210,436
Depreciation, depletion and amortization                 16,929 19,913 25,596
Operating income (loss) 35,951 8,104 11,666 21,503 2,261 15,594 38,632 30,106 77,225 86,593 132,561
Interest income                 73 145 184
Income taxes                 34,115 81,813 93,468
Bad debt and other expenses                 3,326 1,621 4,448
Impairment of proved properties                   7,620 4,975
Additions to properties and equipment                 53,691 46,366 32,966
Long lived assets 138,524       106,608       138,524 106,608 99,848
Total assets 308,167       267,956       308,167 267,956 275,015
Operating Segments | Corporate and Other
                      
Segment Reporting Information [Line Items]                      
Depreciation, depletion and amortization                 63 59 50
Operating income (loss)                 (5,915) (8,405) (9,088)
Interest income                 33 86 104
Additions to properties and equipment                 47 77 60
Long lived assets 152       166       152 166 147
Total assets 20,211       38,585       20,211 38,585 45,986
Operating Segments | Gabon
                      
Segment Reporting Information [Line Items]                      
Revenues                 167,386 192,489 208,781
Depreciation, depletion and amortization                 15,310 15,954 23,604
Operating income (loss)                 98,795 147,985 155,550
Interest income                 40 60 80
Income taxes                 34,115 81,813 93,468
Bad debt and other expenses                 1,764    
Additions to properties and equipment                 53,015 22,731 8,528
Long lived assets 109,597       71,225       109,597 71,225 68,965
Total assets 256,033       190,652       256,033 190,652 185,341
Operating Segments | Angola
                      
Segment Reporting Information [Line Items]                      
Depreciation, depletion and amortization                 28 28 20
Operating income (loss)                 (3,018) (3,293) (6,221)
Interest income                   (1)  
Bad debt and other expenses                 1,562 1,621 4,448
Additions to properties and equipment                 629   7
Long lived assets 11,540       10,938       11,540 10,938 10,964
Total assets 12,204       11,405       12,204 11,405 21,452
Operating Segments | Equatorial Guinea
                      
Segment Reporting Information [Line Items]                      
Operating income (loss)                 (768) (754)  
Additions to properties and equipment                   10,000  
Long lived assets 10,000       10,000       10,000 10,000  
Total assets 10,059       10,000       10,059 10,000  
Operating Segments | USA
                      
Segment Reporting Information [Line Items]                      
Revenues                   2,798 1,655
Depreciation, depletion and amortization                   3,872 1,922
Operating income (loss)                   (48,940) (7,680)
Impairment of proved properties                   7,620 4,975
Additions to properties and equipment                   13,558 24,371
Long lived assets         14,279         14,279 19,772
Total assets         $ 17,314         $ 17,314 $ 22,236