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v2.4.1.9

Property And Equipment (Narrative) (Details) (USD $) | 3 Months Ended | 1 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Jan. 31, 2013 | Dec. 31, 2014 | Oct. 31, 2012 | Oct. 11, 2012 | May 07, 2012
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |
Cumulative capitalization of general and administrative costs incurred and capitalized to the full cost pool | $ 79,900,000 gpor_CumulativeCapitalizationOfGeneralAndAdministrativeCostsIncurredAndCapitalizedToFullCostPool |  |  |  |  |  |
Capitalized general and administrative costs | 7,200,000 gpor_CapitalizedGeneralAndAdministrativeCosts | 6,300,000 gpor_CapitalizedGeneralAndAdministrativeCosts |  |  |  |  |
Capitalized costs of oil and natural gas properties excluded from amortization | 1,546,804,000 us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative |  |  | 1,465,538,000 us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative |  |  |
Payment received from Diamondback | (24,178,000)us-gaap_IncreaseDecreaseInAccountsReceivable | 27,944,000 us-gaap_IncreaseDecreaseInAccountsReceivable |  |  |  |  |
Diamondback [Member] |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |
Investment (shares) |  |  |  |  |  | 7,914,036 us-gaap_InvestmentOwnedBalanceShares / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gpor_DiamondbackMember |
Promissory note receivable |  |  |  |  |  | 63,600,000 us-gaap_NotesAndLoansReceivableNetCurrent / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gpor_DiamondbackMember |
Ownership interest |  |  |  |  | 21.40%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gpor_DiamondbackMember |  | 35.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gpor_DiamondbackMember
Diamondback [Member] | Accounts Receivable - Related Party [Member] |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |
Payment received from Diamondback |  |  | $ 18,600,000 us-gaap_IncreaseDecreaseInAccountsReceivable / us-gaap_BalanceSheetLocationAxis = gpor_AccountsReceivableRelatedPartyMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = gpor_DiamondbackMember |  |  |  |
Minimum [Member] |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |
Expected number of years amortization will commence | 3 years |  |  |  |  |  |
Maximum [Member] |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |
Expected number of years amortization will commence | 5 years |  |  |  |  |  |

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- Definition The sum of the capitalized costs incurred, as of the balance sheet date, of unproved properties excluded from amortization including acquisition costs, exploration costs, development costs, and production costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-10.(c)(7)(ii)) -URI http://asc.fasb.org/extlink&oid=50486907&loc=d3e511914-122862 + Details
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