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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 | $ 13,300,000 us-gaap_ResultsOfOperationsDryHoleCosts | $ 23,900,000 us-gaap_ResultsOfOperationsDryHoleCosts | $ 37,300,000 us-gaap_ResultsOfOperationsDryHoleCosts |  |  |
Future development costs | 52,800,000 us-gaap_CostsIncurredDevelopmentCosts |  |  |  |  |
Development cost to company | 14,800,000 egy_DevelopmentCostToCompany |  |  |  |  |
Oil |  |  |  |  |  |
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items] |  |  |  |  |  |
Proved Developed Reserves | 3,224 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember | 3,305 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember | 3,750 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember | 3,305 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 3,854 us-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 | 1,406,000 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | 1,333,000 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | 1,544,000 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | 1,333,000 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember |  | 856,000 us-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 | 1,500 us-gaap_ProvedDevelopedReservesVolume / dei_LegalEntityAxis = egy_AvoumaAndSouthTchibalaMember |  | 1,200 us-gaap_ProvedDevelopedReservesVolume / dei_LegalEntityAxis = egy_AvoumaAndSouthTchibalaMember |  |  |
Etame |  |  |  |  |  |
Costs Incurred Oil And Gas Property Acquisition Exploration And Development Activities [Line Items] |  |  |  |  |  |
Proved Developed Reserves | 1,100 us-gaap_ProvedDevelopedReservesVolume / dei_LegalEntityAxis = egy_EtameMember | 800 us-gaap_ProvedDevelopedReservesVolume / dei_LegalEntityAxis = egy_EtameMember | 1,000 us-gaap_ProvedDevelopedReservesVolume / dei_LegalEntityAxis = egy_EtameMember | 800 us-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 | 300 us-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 | 36,800,000 egy_AmountInCostAccountForCompany / dei_LegalEntityAxis = egy_ConsortiumMember |  |  |  |  |
Cost Recovered | 907,400 egy_CostRecoveredQuantity / dei_LegalEntityAxis = egy_ConsortiumMember | 929,400 egy_CostRecoveredQuantity / dei_LegalEntityAxis = egy_ConsortiumMember | 367,000 egy_CostRecoveredQuantity / dei_LegalEntityAxis = egy_ConsortiumMember |  |  |
Theoretical Cost | 935,800 egy_TheoreticalCostQuantity / dei_LegalEntityAxis = egy_ConsortiumMember | 1,079,300 egy_TheoreticalCostQuantity / dei_LegalEntityAxis = egy_ConsortiumMember | 1,197,000 egy_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 | 36,400,000 egy_AmountInCostAccountForCompany / dei_LegalEntityAxis = egy_MutambaIroruMember |  |  |  |  |
Proved reserves | 0 egy_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 | 0 egy_ProvedReserves / dei_LegalEntityAxis = egy_BlockFiveProductionMember |  |  |  |  |
Royalty Payments | 0 us-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 | 0 egy_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 |  |  |  | 11,700,000 us-gaap_ResultsOfOperationsDryHoleCosts / us-gaap_StatementGeographicalAxis = country_GA |  |
Unsuccessful exploration wells | 1 us-gaap_DevelopmentWellsDrilledNetNonproductive / us-gaap_StatementGeographicalAxis = country_GA |  |  |  |  |
Exploration license |  |  |  | 1,600,000 us-gaap_ResultsOfOperationsExpenseOther / us-gaap_StatementGeographicalAxis = country_GA |  |
Contractual price | 98.88 egy_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 |  |  |  |  | 10,000,000 us-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 | $ 8,000 us-gaap_CostsIncurredDevelopmentCosts / us-gaap_StatementGeographicalAxis = country_US | $ 113,000 us-gaap_CostsIncurredDevelopmentCosts / us-gaap_StatementGeographicalAxis = country_US | $ 9,689,000 us-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 | 86.49 egy_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 | 5.19 egy_ContractualPricePerUnit / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember / us-gaap_StatementGeographicalAxis = country_US |  |  |  |  |

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