Annual report pursuant to Section 13 and 15(d)

Summary Of Significant Accounting Policies (Narrative) (Detail)

v3.3.1.900
Summary Of Significant Accounting Policies (Narrative) (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Impairment Of Oil And Gas Properties $ 8,800,000 $ 0 $ 600,000 $ 2,700,000 $ 2,300,000 $ 0 $ 800,000 $ 800,000      
Asset Impairment Charges 52,100,000 18,000,000 5,800,000 5,400,000 98,300,000       $ 81,322,000 $ 98,341,000  
Oil And Gas Sales Revenue 17,523,000 [1] 17,546,000 [1] 27,137,000 [1] 18,239,000 [1] 23,037,000 [1] 24,486,000 [1] 52,098,000 [1] 28,071,000 [1] 80,445,000 127,691,000 $ 169,277,000
Net Income Loss (80,779,000) (33,668,000) $ (5,204,000) $ (39,005,000) (98,332,000) $ 3,109,000 $ 24,711,000 $ (7,038,000) (158,656,000) (77,550,000) 43,072,000
Recorded allowance                 2,699,000 2,400,000 1,562,000
Gas imbalance receivable 0       $ 0       0 0  
Gains or Loss on foreign currency transactions                 1,500,000 (700,000) (100,000)
Other operating loss, net                 $ (2,948,000)    
Group 42-BLR Group [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Percentage owned by shareholder group                 11.10%    
Legal expense                 $ 350,000    
Scenario, Adjustment Related to Prior Period [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Impairment Of Oil And Gas Properties                   7,000,000  
Oil And Gas Sales Revenue (2,300,000)                    
Net Income Loss                   77,600,000  
Scenario, Adjustment [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Impairment Of Oil And Gas Properties   $ 3,600,000             7,000,000    
Scenario, Actual [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Impairment Of Oil And Gas Properties                   98,300,000  
Gabon [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Recorded allowance                 2,700,000 $ 2,400,000  
Gabon [Member] | Scenario, Adjustment [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Oil And Gas Sales Revenue (2,300,000)                    
Angola [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Impairment Of Oil And Gas Properties                 $ 8,200,000    
Recorded allowance                     $ 1,600,000
Gabon And Angola [Member]                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Other operating loss, net $ (3,300,000)                    
Office Equipment                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Estimated useful life                 5 years    
Minimum [Member] | Leasehold Improvements                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Estimated useful life                 5 years    
Maximum [Member] | Leasehold Improvements                      
Error Corrections and Prior Period Adjustments Restatement [Line Items]                      
Estimated useful life                 7 years    
[1] As discussed in Note 3 to the consolidated financial statements an error was identified the prepaid royalty account that caused previous periods to be misstated. Total revenues were corrected through an out of period adjustment in the fourth quarter of 2015 with reduction of $2.3 million, overstating operating loss and net loss by $2.3 million.