Annual report pursuant to Section 13 and 15(d)

Supplemental Information On Oil And Gas Producing Activities (Narrative) (Detail)

v3.3.1.900
Supplemental Information On Oil And Gas Producing Activities (Narrative) (Detail)
 12 Months Ended
Dec. 31, 2015
USD ($)
$ / Boe
$ / Mcfe
MMcf
MBbls
Dec. 31, 2014
USD ($)
MMcf
MBbls
Dec. 31, 2013
USD ($)
MMcf
MBbls
Dec. 31, 2012
MMcf
MBbls
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Years of production lost due to lower oil prices 3 years 6 months      
Lower Oil Prices [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Revisions of previous estimates 2,705      
Removal Of Sour Reserves [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Revisions of previous estimates 1,440      
Exceeding Expectations [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Revisions of previous estimates 370      
Oil [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Proved Developed Reserves 2,855 3,224 3,305 3,750
Revisions of previous estimates (3,746) 2,312 771  
Proved reserves 2,855 8,260 7,232 7,488
Gas [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Proved Developed Reserves | MMcf 1,053 1,406 1,333 1,544
Revisions of previous estimates | MMcf [1] (172) 300 114  
Proved reserves | MMcf [1] 1,053 1,406 1,333 1,544
Consortium [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Cost account recovery percentage 70.00%      
Net cost account | $ $ 87,900,000      
Consortium [Member] | Minimum [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Profit oil payment percentage 50.00%      
Consortium [Member] | Maximum [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Profit oil payment percentage 60.00%      
Gabon [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Fixed royalty rate 13.00%      
Gabon [Member] | Oil [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Average price for reverse estimate | $ / Boe 49.36      
United States [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Future development costs | $   $ 8,000 $ 113,000  
United States [Member] | Oil [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Average price for reverse estimate | $ / Boe 40.43      
United States [Member] | Gas [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Average price for reverse estimate | $ / Mcfe 2.35      
Avouma and South Tchibala [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Period of development 20 years      
Avouma and South Tchibala [Member] | Better Performance [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Revisions of previous estimates   1,500    
Etame [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Period of development 20 years      
Etame [Member] | Better Performance [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Revisions of previous estimates   1,100    
Etame [Member] | Revised For 2014 [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Revisions of previous estimates     800  
Ebouri [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Period of development 20 years      
Ebouri [Member] | Uneconomic [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Revisions of previous estimates   300    
Mutamba Iroru [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Cost account recovery percentage 70.00%      
Proved reserves 0      
Block 5 Production [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Cost account recovery percentage 50.00%      
Proved reserves 0      
Period of development 20 years      
Royalty Payments | $ $ 0      
Block P Production [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Cost account recovery percentage 70.00%      
Proved reserves 0      
Period of development 25 years      
Income tax on net profits 25.00%      
Block P Production [Member] | Minimum [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Fixed royalty rate 10.00%      
Profit oil payment percentage 10.00%      
Block P Production [Member] | Maximum [Member]        
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]        
Fixed royalty rate 16.00%      
Profit oil payment percentage 60.00%      
[1] The natural gas reserves shown as of December 31, 2015 include natural gas liquids ("NGL") expressed as gas volumes using a ratio of 4.9 MMcf to 1 MBbl of NGL.