Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Gas Producing Activities - Additional Information (Detail)

v2.4.0.8
Supplemental Information on Oil and Gas Producing Activities - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Exploration expense $ 23,900,000 $ 37,300,000 $ 100,000
Percentage of working interest acquired 31.00%    
Acquisition of Working Interest, cost 10,000,000    
Asset retirement cost 5,200,000 4,700,000 10,400,000
Future development costs 52,800,000    
Development cost to company 14,800,000    
Minimum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Net share that the consortium receives from production, Minimum 67.70%    
Maximum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Net share that the consortium receives from production, Maximum 82.50%    
United States
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Unsuccessful exploration wells 2    
Future development costs 113,000 9,689,000 14,936,000
United States | Oil
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Contractual price 87.61    
United States | Gas
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Contractual price 4.51    
Foreign Tax Authority
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Unsuccessful exploration wells 3    
Future development costs 54,420,000 4,022,000 8,011,000
Contractual price 107.69    
Fixed royalty rate 13.00%    
Consortium
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of production 70.00%    
Net cost account 30,100,000    
Production Rate Maximum 25,000    
Production rate, Minimum 5,000    
Cost Recovered 929,400 367,000 304,000
Theoretical Cost 1,079,300 1,197,000 1,303,000
Consortium | Minimum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of contract area, Minimum 50.00%    
Consortium | Maximum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of contract area, Maximum 60.00%    
Etame
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Period of development 20 years    
Expiration of development expire in 2021    
Exploration area expiration year expires in July 2014    
Avouma
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Period of development 20 years    
Expiration of development expire in 2025    
Ebouri
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Period of development 20 years    
Expiration of development expire in 2026    
Mutamba Iroru
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of production 70.00%    
Net cost account 36,400,000    
Production Rate Maximum 20,000    
Production rate, Minimum 7,500    
Proved reserves 0    
Mutamba Iroru | Minimum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of contract area, Minimum 50.00%    
Net share that the consortium receives from production, Minimum 72.00%    
Mutamba Iroru | Maximum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of contract area, Maximum 63.00%    
Net share that the consortium receives from production, Maximum 85.00%    
Block 5 Production
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of production 50.00%    
Period of development 20 years    
Proved reserves 0    
Royalty Payments 0    
Block 5 Production | Minimum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of contract area, Minimum 30.00%    
Block 5 Production | Maximum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of contract area, Maximum 90.00%    
Block P Production
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Percentage of production 70.00%    
Period of development 25 years    
Proved reserves $ 0    
Income tax on net profits 25.00%    
Block P Production | Minimum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Fixed royalty rate 10.00%    
Percentage of contract area, Minimum 10.00%    
Block P Production | Maximum
      
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]      
Fixed royalty rate 16.00%    
Percentage of contract area, Maximum 60.00%