Annual report pursuant to Section 13 and 15(d)

Capitalization of Exploratory Well Costs - Additional Information (Detail)

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Capitalization of Exploratory Well Costs - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Accounting Standards Update 2010-03
 
Capitalized Costs Relating To Oil And Gas Producing Activities By Geographic Area [Line Items]  
Accounting Standard Code for Extractive Industries followed for capitalization purposes - ASC Topic 932 ASC Topic 932 - Extractive Industries provides that an exploratory well shall be capitalized as part of the entity’s uncompleted wells pending the determination of whether the well has found proved reserves. Further, an exploration well that discovers oil and gas reserves, but those reserves cannot be classified as proved when drilling is completed, shall be capitalized if the well has found a sufficient quantity of reserves to justify its completion as a producing well and the entity is making sufficient progress assessing the reserves and the economic and operating viability of the project. If either condition is not met, the exploration well would be assumed to be impaired and its costs would be charged to expense.
Etame Marin
 
Capitalized Costs Relating To Oil And Gas Producing Activities By Geographic Area [Line Items]  
Number of side tracks 2
Area of sand of oil 5
North Tchibala
 
Capitalized Costs Relating To Oil And Gas Producing Activities By Geographic Area [Line Items]  
Capitalization on development plan $ 7.8
Mutamba Iroru
 
Capitalized Costs Relating To Oil And Gas Producing Activities By Geographic Area [Line Items]  
Number of side tracks 3
Capitalization on development plan $ 8.9