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Capitalization of Exploratory Well Costs - Additional Information (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
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. |  |
Dry hole costs and impairment loss on unproved leasehold | $ 13,273,000 us-gaap_ExplorationAbandonmentAndImpairmentExpense | $ 22,490,000 us-gaap_ExplorationAbandonmentAndImpairmentExpense | $ 37,289,000 us-gaap_ExplorationAbandonmentAndImpairmentExpense
Etame Marin |  |  |
Capitalized Costs Relating To Oil And Gas Producing Activities By Geographic Area [Line Items] |  |  |
Number of side tracks | 2 egy_NumberOfSideTracks / us-gaap_StatementGeographicalAxis = egy_FieldOneMember |  |
Area of sand of oil | 5 egy_AreaOfSandOfOil / us-gaap_StatementGeographicalAxis = egy_FieldOneMember |  |
Southeast Etame Field |  |  |
Capitalized Costs Relating To Oil And Gas Producing Activities By Geographic Area [Line Items] |  |  |
Dry hole costs and impairment loss on unproved leasehold | 7,800,000 us-gaap_ExplorationAbandonmentAndImpairmentExpense / us-gaap_StatementGeographicalAxis = egy_SoutheastEtameFieldMember |  |
Mutamba Iroru |  |  |
Capitalized Costs Relating To Oil And Gas Producing Activities By Geographic Area [Line Items] |  |  |
Number of side tracks | 3 egy_NumberOfSideTracks / us-gaap_StatementGeographicalAxis = egy_MutambaIroruMember |  |
Capitalization on development plan | $ 8,900,000 us-gaap_CapitalizedExploratoryWellCostAdditionsPendingDeterminationOfProvedReserves / us-gaap_StatementGeographicalAxis = egy_MutambaIroruMember |  |

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- Definition Additions to capitalized exploratory well costs that were added during the reporting period pending the determination of proved reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447 + Details
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- Definition Interim financial statement disclosure that includes information about any significant change in the information disclosed in the most recent annual financial statements related to capitalized exploratory well costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447 + Details
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- Definition The adjustment to expense previously capitalized costs of drilling exploratory wells when proved reserves are not found or when the entity obtains information that raises substantial doubt about the economic or operational viability of the project. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 40 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6475089&loc=d3e66625-109467 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 35 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28370743&loc=d3e66150-109466 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 40 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6475089&loc=d3e66584-109467 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 40 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6475089&loc=d3e66610-109467 + Details
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