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v2.4.1.9

Fair Value Measurements (Details) (USD $) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Asset retirement obligation capitalized | $ 1,584,000 us-gaap_AssetRetirementObligationLiabilitiesIncurred | $ 1,869,000 us-gaap_AssetRetirementObligationLiabilitiesIncurred |
Mammoth Energy Partners LP [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Equity investment |  |  | 143,500,000 us-gaap_EquityMethodInvestmentsFairValueDisclosure / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember
Level 1 [Member] | Fixed Price Swaps [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fixed price swaps | 134,986,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = gpor_FixedPriceSwapsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |  |
Fixed price swaps | 823,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = gpor_FixedPriceSwapsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member |  |
Level 2 [Member] | Fixed Price Swaps [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fixed price swaps | 0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = gpor_FixedPriceSwapsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |  |
Fixed price swaps | 0 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = gpor_FixedPriceSwapsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member |  |
Level 3 [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Asset retirement obligation capitalized | 1,600,000 us-gaap_AssetRetirementObligationLiabilitiesIncurred / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |  |
Level 3 [Member] | Mammoth Energy Partners LP [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Equity investment |  |  | 143,500,000 us-gaap_EquityMethodInvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MammothEnergyPartnersLPMember
Level 3 [Member] | Fixed Price Swaps [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fixed price swaps | 0 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = gpor_FixedPriceSwapsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |  |
Fixed price swaps | $ 0 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = gpor_FixedPriceSwapsMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |  |

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