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Equity Investments (Narrative) (Details) (USD $) | 3 Months Ended | 1 Months Ended | 0 Months Ended | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Mar. 31, 2015 | Jan. 28, 2014 | Nov. 12, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Dec. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2012 | Oct. 11, 2012
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Payments for equity method investments | $ 6,093,000 us-gaap_PaymentsToAcquireEquityMethodInvestments | $ 23,687,000 us-gaap_PaymentsToAcquireEquityMethodInvestments |  |  |  |  |  |  |  |  |
Equity investments and investments in subsidiaries | 374,971,000 us-gaap_EquityMethodInvestments |  | 374,971,000 us-gaap_EquityMethodInvestments |  |  |  |  |  | 369,581,000 us-gaap_EquityMethodInvestments |  |
(Income) loss from equity method investments | (19,975,000)us-gaap_IncomeLossFromEquityMethodInvestments | (128,475,000)us-gaap_IncomeLossFromEquityMethodInvestments |  |  |  |  |  |  |  |  |
Distributions received | 817,000 us-gaap_EquityMethodInvestmentDividendsOrDistributions | 0 us-gaap_EquityMethodInvestmentDividendsOrDistributions |  |  |  |  |  |  |  |  |
Apico Llc [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Equity shares owned by affiliate (shares) | 85,122 gpor_EquitySharesOwnedByAffiliateOfInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_ApicoLlcMember |  |  |  |  |  |  |  |  |  |
Total shares owned of subaffiliate (shares) | 1,000,000 gpor_EquityMethodInvestmentTotalSharesOutstandingOfSubaffiliate / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_ApicoLlcMember |  |  |  |  |  |  |  |  |  |
Gas and oil area, reserve (acres) | 243,000 gpor_GasAndOilAreaReserve / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_ApicoLlcMember |  |  |  |  |  |  |  |  |  |
Tatex Thailand III, LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gas and oil area, reserve (acres) | 245,000 gpor_GasAndOilAreaReserve / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_TatexThailandIiiLlcMember |  |  |  |  |  |  |  |  |  |
Ownership interest | 17.90%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_TatexThailandIiiLlcMember |  | 17.90%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_TatexThailandIiiLlcMember |  |  |  |  |  |  |  |
Equity investments and investments in subsidiaries | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_TatexThailandIiiLlcMember |  | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_TatexThailandIiiLlcMember |  |  |  |  |  |  |  |
(Income) loss from equity method investments | 0 us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_TatexThailandIiiLlcMember | 49,000 us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_TatexThailandIiiLlcMember |  |  |  |  |  |  |  |  |
Grizzly Oil Sands ULC [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gas and oil area, reserve (acres) | 830,000 gpor_GasAndOilAreaReserve / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  |  |  |  |  |  |  |  |  |
Cash calls paid | 6,100,000 gpor_EquityMethodInvestmentAmountOfCashCallsBasedOnProportionateOwnershipInterest / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  |  |  |  |  |  |  |  |  |
Increase (decrease) due to foreign currency translation adjustment | 15,000,000 gpor_EquityMethodInvestmentsIncreaseDecreaseDueToForeignCurrencyTranslationAdjustment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 7,300,000 gpor_EquityMethodInvestmentsIncreaseDecreaseDueToForeignCurrencyTranslationAdjustment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  |  |  |  |  |  |  |  |
Ownership interest | 24.9999%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  | 24.9999%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  |  |  |  |  |  |  |
Equity investments and investments in subsidiaries | 167,186,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  | 167,186,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  |  |  |  |  | 180,218,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  |
(Income) loss from equity method investments | 4,142,000 us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 2,001,000 us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember |  |  |  |  |  |  |  |  |
Windsor Midstream LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Ownership interest | 22.50%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_WindsorMidstreamLlcMember |  | 22.50%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_WindsorMidstreamLlcMember |  |  |  |  |  |  |  |
Equity investments and investments in subsidiaries | 32,292,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_WindsorMidstreamLlcMember |  | 32,292,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_WindsorMidstreamLlcMember |  |  |  |  |  | 13,505,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_WindsorMidstreamLlcMember |  |
(Income) loss from equity method investments | (18,787,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_WindsorMidstreamLlcMember | (168,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_WindsorMidstreamLlcMember |  |  |  |  |  |  |  |  |
Windsor Midstream LLC [Member] | MidMar Gas LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  |  |  |  |  |  | 28.40%us-gaap_EquityMethodInvestmentOwnershipPercentage / dei_LegalEntityAxis = gpor_MidmarGasLlcMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_WindsorMidstreamLlcMember |
Coronado Midstream [Member] | Windsor Midstream LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Proceeds from sale of interest in partnership unit |  |  | 600,000,000 us-gaap_ProceedsFromSaleOfEquityMethodInvestments / dei_LegalEntityAxis = gpor_WindsorMidstreamLlcMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_CoronadoMidstreamMember |  |  |  |  |  |  |  |
Gain on sale on investment |  |  | 85,500,000 us-gaap_GainLossOnSaleOfEquityInvestments / dei_LegalEntityAxis = gpor_WindsorMidstreamLlcMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_CoronadoMidstreamMember |  |  |  |  |  |  |  |
Blackhawk Midstream LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Ownership interest | 48.50%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  | 48.50%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  |  |  |  |  |  |  |
Equity investments and investments in subsidiaries | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  |  |  |  |  | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  |
(Income) loss from equity method investments | (7,217,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember | (84,787,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  |  |  |  |  |  |  |  |
Blackhawk Midstream LLC [Member] | Ohio Gathering Company, LLC and Ohio Condensate Company, LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Purchase price of sold equity interests |  |  |  | 190,000,000 us-gaap_ProceedsFromDivestitureOfBusinesses / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = gpor_OhioGatheringCompanyLLCandOhioCondensateCompanyLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  |  |  |  |  |  |
Amount put in escrow |  |  |  | 14,300,000 us-gaap_EscrowDeposit / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = gpor_OhioGatheringCompanyLLCandOhioCondensateCompanyLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  |  |  |  |  |  |
Proceeds from release of escrow deposits | 7,200,000 us-gaap_EscrowDepositDisbursementsRelatedToPropertyAcquisition1 / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = gpor_OhioGatheringCompanyLLCandOhioCondensateCompanyLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  |  |  |  |  |  |  |  |  |
Distributions received |  | 84,800,000 us-gaap_EquityMethodInvestmentDividendsOrDistributions / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = gpor_OhioGatheringCompanyLLCandOhioCondensateCompanyLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_BlackhawkMidstreamLlcMember |  |  |  |  |  |  |  |  |
Diamondback Energy, Inc [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Ownership interest | 0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  | 0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  |  |  |  |  |  |  |
Investment (shares) |  |  |  |  |  |  |  |  |  |  | 7,914,036 us-gaap_InvestmentOwnedBalanceShares / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Equity investments and investments in subsidiaries | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  |  |  |  |  | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  | 138,500,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Number of shares issued in transaction (shares) |  |  |  |  | 942,000 us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 1,437,500 us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 1,000,000 us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 4,534,536 us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  |  |
Proceeds received from sale of stock |  |  |  |  | 60,800,000 us-gaap_SaleOfStockConsiderationReceivedOnTransaction / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 197,600,000 us-gaap_SaleOfStockConsiderationReceivedOnTransaction / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  | 192,700,000 us-gaap_SaleOfStockConsiderationReceivedOnTransaction / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  |  |
(Income) loss from equity method investments | 0 us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (48,767,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember |  |  |  |  |  |  |  |  |
Sturgeon Acquisitions LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Payments for equity method investments |  |  |  |  |  |  |  |  | 20,700,000 us-gaap_PaymentsToAcquireEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  |
Ownership interest | 25.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  | 25.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  |  |  |  |  | 25.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  |
Equity investments and investments in subsidiaries | 22,258,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  | 22,258,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  |  |  |  |  | 22,507,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  |
(Income) loss from equity method investments | (568,000)us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember | 0 us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  |  |  |  |  |  |  |  |
Distributions received | 800,000 us-gaap_EquityMethodInvestmentDividendsOrDistributions / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SturgeonAcquisitionsLLCMember |  |  |  |  |  |  |  |  |  |
Mammoth Energy Partners LP [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |
Ownership interest | 30.50%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember |  | 30.50%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember |  |  |  |  |  | 30.50%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember |  |
Equity investments and investments in subsidiaries | 143,807,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember |  | 143,807,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember |  |  |  |  |  | 143,973,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember |  |
(Income) loss from equity method investments | 2,372,000 us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember | 0 us-gaap_IncomeLossFromEquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember |  |  |  |  |  |  |  |  |
Equity investment in Mammoth Energy Partners |  |  |  |  |  |  |  |  | $ 143,500,000 us-gaap_EquityMethodInvestmentsFairValueDisclosure / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember |  |

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- Definition The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes and insurance obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments. This element excludes replacement reserves which are an escrow separately provided for within the US GAAP taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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