Annual report pursuant to Section 13 and 15(d)

Commitments And Contingencies (Narrative) (Detail)

v3.3.1.900
Commitments And Contingencies (Narrative) (Detail)
a in Millions
 1 Months Ended 3 Months Ended 12 Months Ended 50 Months Ended
Mar. 14, 2016
USD ($)
Nov. 30, 2006
USD ($)
item
Mar. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Sep. 30, 2015
USD ($)
Jun. 30, 2015
USD ($)
Mar. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Sep. 30, 2014
USD ($)
Jun. 30, 2014
USD ($)
Mar. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 31, 2015
USD ($)
a
item
$ / Boe
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
$ / Boe
Dec. 31, 2010
km²
Dec. 31, 2012
USD ($)
Commitments And Contingencies [Line Items]                                  
Expected settlement of litigation       $ 550,000                 $ 550,000        
Litigation, accrued expected recoveries       0                 $ 0        
Period of Charter                         2 years        
Percentage of share in charter payment                         28.10%        
Liabilities, guarantees' fair value       1,000,000       $ 1,000,000         $ 1,000,000 $ 1,000,000      
Charter fee for production up to 20,000 BOPD | $ / Boe                         0.93   0.25    
Charter fee for those bbls produced in exess of 20,000 BOPD | $ / Boe                         2.50        
Company's share of charter expense                         $ 10,900,000 11,800,000 $ 10,400,000    
Rent expense, operating leases                         4,700,000 4,000,000 4,100,000    
Abandonment funding       5,137,000       3,537,000         5,137,000 3,537,000      
Allowance for accounts with partners               7,600,000           7,600,000      
Accounts with partners, net of allowance       27,856,000       10,903,000         27,856,000 10,903,000      
Recorded restricted cash       15,830,000       20,830,000         15,830,000 20,830,000      
Exploration expense                         46,453,000 15,358,000 23,928,000    
Dry hole costs and impairment loss on unproved leasehold         $ 9,000,000   $ 24,500,000     $ 2,000,000 $ 9,700,000   45,652,000 13,273,000 22,490,000    
Asset retirement obligations       16,166,000       14,846,000       $ 11,464,000 16,166,000 14,846,000 11,464,000   $ 10,368,000
Impairment of Oil and Gas Properties       8,800,000 $ 0 $ 600,000 $ 2,700,000 $ 2,300,000 $ 0 $ 800,000 $ 800,000            
Inventory write-off       3,400,000                          
Gabon Taxation Department [Member]                                  
Commitments And Contingencies [Line Items]                                  
Tax examination settlement payment       300,000                 300,000        
Sonangol P&P [Member]                                  
Commitments And Contingencies [Line Items]                                  
Accounts with partners, net of allowance       8,100,000                 $ 8,100,000        
Scenario, Forecast [Member] | Sonangol P&P [Member]                                  
Commitments And Contingencies [Line Items]                                  
Reversal of allowance     $ 7,600,000                            
Interst income     $ 3,200,000                            
Gabon [Member]                                  
Commitments And Contingencies [Line Items]                                  
Discount                         25.00%        
Contractual Obligation Company Share                         $ 2,300,000 $ 3,300,000 $ 3,000,000    
Contractual Obligation accrued amount       1,800,000                 1,800,000        
Offshore Gabon [Member]                                  
Commitments And Contingencies [Line Items]                                  
Drilling rig cost day rate                         172,000        
Remaining commitment of drilling activity       32,200,000                 32,200,000        
Remaining commitment of drilling activity, net       9,800,000                 $ 9,800,000        
Percentage of annual funding over seven years                         12.14%        
Funding period for initial rate                         7 years        
Second funding period of production license                         3 years        
Percentage of annual funding over last three years                         5.00%        
Abandonment cost related to annual funding                         $ 61,100,000        
Abandonment cost related to annual funding, net                         $ 17,300,000        
Funding period abandonment funding                         10 years        
Abandonment funding, gross       18,300,000                 $ 18,300,000        
Abandonment funding       5,100,000                 $ 5,100,000        
Number of contract extension periods | item                         2        
Production license agreement term extended by government                         5 years        
Angola [Member]                                  
Commitments And Contingencies [Line Items]                                  
Cost related to drilling   $ 29,500,000                              
Drilling cost to company   $ 14,800,000                              
Area under acquire property exploration rights agreement term (acres) | a                         1.4        
Additional joint operation agreement related to third party in working interest percentage                         10.00%        
Production license agreement term                         4 years        
Extended drilling period                         1 year        
Number of additional exploration wells due to exploration period extension | item                         2        
Production license agreement term extended by government                         3 years        
Recorded restricted cash       15,000,000                 $ 15,000,000        
Working interest ownership, percentage   40.00%                              
Impairment of Oil and Gas Properties                         8,200,000        
Inventory write-off                         1,900,000        
Number of wells drilling commitment | item   2                              
Working interest ownership other, percentage                       40.00%          
Drilling commitment, gross       10,000,000                 10,000,000        
Drilling commitment, net       $ 5,000,000                 $ 5,000,000        
Angola [Member] | Seismic Obligation [Member]                                  
Commitments And Contingencies [Line Items]                                  
Length of acquired property | km²                               1,000  
Subsequent Event [Member] | Sonangol P&P [Member]                                  
Commitments And Contingencies [Line Items]                                  
Interest receivable $ 3,200,000                                
Accounts with partners, net of allowance 7,600,000                                
Joint interest owner payments $ 19,000,000