Annual report pursuant to Section 13 and 15(d)

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

v2.4.1.9
Supplemental Information on Oil and Gas Producing Activities - Additional Information (Detail) (USD $)
12 Months Ended 3 Months Ended 1 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2013
Nov. 30, 2012
Dec. 31, 2011
MBbls
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Exploration expense $ 13,300,000us-gaap_ResultsOfOperationsDryHoleCosts $ 23,900,000us-gaap_ResultsOfOperationsDryHoleCosts $ 37,300,000us-gaap_ResultsOfOperationsDryHoleCosts      
Future development costs 52,800,000us-gaap_CostsIncurredDevelopmentCosts          
Development cost to company 14,800,000egy_DevelopmentCostToCompany          
Oil            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Proved Developed Reserves 3,224us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_OilReservesMember
3,305us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_OilReservesMember
3,750us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_OilReservesMember
3,305us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_OilReservesMember
  3,854us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_OilReservesMember
Gas            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Proved Developed Reserves 1,406,000us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_NaturalGasReservesMember
1,333,000us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_NaturalGasReservesMember
1,544,000us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_NaturalGasReservesMember
1,333,000us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_NaturalGasReservesMember
  856,000us-gaap_ProvedDevelopedReservesVolume
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_NaturalGasReservesMember
Avouma and South Tchibala            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Proved Developed Reserves 1,500us-gaap_ProvedDevelopedReservesVolume
/ dei_LegalEntityAxis
= egy_AvoumaAndSouthTchibalaMember
  1,200us-gaap_ProvedDevelopedReservesVolume
/ dei_LegalEntityAxis
= egy_AvoumaAndSouthTchibalaMember
     
Etame            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Proved Developed Reserves 1,100us-gaap_ProvedDevelopedReservesVolume
/ dei_LegalEntityAxis
= egy_EtameMember
800us-gaap_ProvedDevelopedReservesVolume
/ dei_LegalEntityAxis
= egy_EtameMember
1,000us-gaap_ProvedDevelopedReservesVolume
/ dei_LegalEntityAxis
= egy_EtameMember
800us-gaap_ProvedDevelopedReservesVolume
/ dei_LegalEntityAxis
= egy_EtameMember
   
Period of development 20 years          
Expiration of development expire in 2021          
Exploration area expiration year expired in July 2014          
Ebouri            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Proved Developed Reserves 300us-gaap_ProvedDevelopedReservesVolume
/ dei_LegalEntityAxis
= egy_EbouriMember
         
Period of development 20 years          
Expiration of development expire in 2026          
Consortium            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of production 70.00%egy_PercentageOfProductionRemainingAfterDeductingRoyalty
/ dei_LegalEntityAxis
= egy_ConsortiumMember
         
Net cost account 36,800,000egy_AmountInCostAccountForCompany
/ dei_LegalEntityAxis
= egy_ConsortiumMember
         
Cost Recovered 907,400egy_CostRecoveredQuantity
/ dei_LegalEntityAxis
= egy_ConsortiumMember
929,400egy_CostRecoveredQuantity
/ dei_LegalEntityAxis
= egy_ConsortiumMember
367,000egy_CostRecoveredQuantity
/ dei_LegalEntityAxis
= egy_ConsortiumMember
     
Theoretical Cost 935,800egy_TheoreticalCostQuantity
/ dei_LegalEntityAxis
= egy_ConsortiumMember
1,079,300egy_TheoreticalCostQuantity
/ dei_LegalEntityAxis
= egy_ConsortiumMember
1,197,000egy_TheoreticalCostQuantity
/ dei_LegalEntityAxis
= egy_ConsortiumMember
     
Consortium | Minimum            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of contract area 50.00%egy_PercentageOfContractArea
/ dei_LegalEntityAxis
= egy_ConsortiumMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
         
Consortium | Maximum            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of contract area 60.00%egy_PercentageOfContractArea
/ dei_LegalEntityAxis
= egy_ConsortiumMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
         
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          
Mutamba Iroru            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of production 70.00%egy_PercentageOfProductionRemainingAfterDeductingRoyalty
/ dei_LegalEntityAxis
= egy_MutambaIroruMember
         
Net cost account 36,400,000egy_AmountInCostAccountForCompany
/ dei_LegalEntityAxis
= egy_MutambaIroruMember
         
Proved reserves 0egy_ProvedReserves
/ dei_LegalEntityAxis
= egy_MutambaIroruMember
         
Mutamba Iroru | Minimum            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of contract area 50.00%egy_PercentageOfContractArea
/ dei_LegalEntityAxis
= egy_MutambaIroruMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
         
Mutamba Iroru | Maximum            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of contract area 63.00%egy_PercentageOfContractArea
/ dei_LegalEntityAxis
= egy_MutambaIroruMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
         
Block 5 Production            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of production 50.00%egy_PercentageOfProductionRemainingAfterDeductingRoyalty
/ dei_LegalEntityAxis
= egy_BlockFiveProductionMember
         
Period of development 20 years          
Proved reserves 0egy_ProvedReserves
/ dei_LegalEntityAxis
= egy_BlockFiveProductionMember
         
Royalty Payments 0us-gaap_RoyaltyExpense
/ dei_LegalEntityAxis
= egy_BlockFiveProductionMember
         
Block 5 Production | Minimum            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of contract area 30.00%egy_PercentageOfContractArea
/ dei_LegalEntityAxis
= egy_BlockFiveProductionMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
         
Block 5 Production | Maximum            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of contract area 90.00%egy_PercentageOfContractArea
/ dei_LegalEntityAxis
= egy_BlockFiveProductionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
         
Block P Production            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of production 70.00%egy_PercentageOfProductionRemainingAfterDeductingRoyalty
/ dei_LegalEntityAxis
= egy_BlockPProductionMember
         
Period of development 25 years          
Proved reserves 0egy_ProvedReserves
/ dei_LegalEntityAxis
= egy_BlockPProductionMember
         
Income tax on net profits 25.00%egy_RateOfIncomeTaxOnNetProfits
/ dei_LegalEntityAxis
= egy_BlockPProductionMember
         
Block P Production | Minimum            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Fixed royalty rate 10.00%egy_RateOfFixedRoyaltyPayableUnderProductionSharingContract
/ dei_LegalEntityAxis
= egy_BlockPProductionMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
         
Percentage of contract area 10.00%egy_PercentageOfContractArea
/ dei_LegalEntityAxis
= egy_BlockPProductionMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
         
Block P Production | Maximum            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Fixed royalty rate 16.00%egy_RateOfFixedRoyaltyPayableUnderProductionSharingContract
/ dei_LegalEntityAxis
= egy_BlockPProductionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
         
Percentage of contract area 60.00%egy_PercentageOfContractArea
/ dei_LegalEntityAxis
= egy_BlockPProductionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
         
Gabon            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Exploration expense       11,700,000us-gaap_ResultsOfOperationsDryHoleCosts
/ us-gaap_StatementGeographicalAxis
= country_GA
   
Unsuccessful exploration wells 1us-gaap_DevelopmentWellsDrilledNetNonproductive
/ us-gaap_StatementGeographicalAxis
= country_GA
         
Exploration license       1,600,000us-gaap_ResultsOfOperationsExpenseOther
/ us-gaap_StatementGeographicalAxis
= country_GA
   
Contractual price 98.88egy_ContractualPricePerUnit
/ us-gaap_StatementGeographicalAxis
= country_GA
         
Fixed royalty rate 13.00%egy_RateOfFixedRoyaltyPayableUnderProductionSharingContract
/ us-gaap_StatementGeographicalAxis
= country_GA
         
Equatorial Guinea            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Percentage of working interest acquired         31.00%egy_PercentageOfWorkingInterestAcquired
/ us-gaap_StatementGeographicalAxis
= country_GQ
 
Acquisition of Working Interest, cost         10,000,000us-gaap_SignificantCostsIncurredToAcquireMineralInterestOfProvedReserves
/ us-gaap_StatementGeographicalAxis
= country_GQ
 
United States            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Future development costs $ 8,000us-gaap_CostsIncurredDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_US
$ 113,000us-gaap_CostsIncurredDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_US
$ 9,689,000us-gaap_CostsIncurredDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_US
     
United States | Oil            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Contractual price 86.49egy_ContractualPricePerUnit
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_OilReservesMember
/ us-gaap_StatementGeographicalAxis
= country_US
         
United States | Gas            
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items]            
Contractual price 5.19egy_ContractualPricePerUnit
/ us-gaap_ReserveQuantitiesByTypeOfReserveAxis
= us-gaap_NaturalGasReservesMember
/ us-gaap_StatementGeographicalAxis
= country_US