| Supplemental Information On Oil And Gas Exploration And Production Activities (Costs Incurred In Oil and Gas Property Acquisition and Development Activities) (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | |
| Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] | |||
| Acquisition | $ 440,288us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties | $ 338,153us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties | $ 513,904us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties | 
| Development of proved undeveloped properties | 864,511us-gaap_CostsIncurredDevelopmentCosts | 408,121us-gaap_CostsIncurredDevelopmentCosts | 121,787us-gaap_CostsIncurredDevelopmentCosts | 
| Exploratory | 2,249us-gaap_CostsIncurredExplorationCosts | 26,174us-gaap_CostsIncurredExplorationCosts | 93,397us-gaap_CostsIncurredExplorationCosts | 
| Recompletions | 45,658gpor_CostsIncurredRecompletionsOfOilAndGasProperties | 44,633gpor_CostsIncurredRecompletionsOfOilAndGasProperties | 24,643gpor_CostsIncurredRecompletionsOfOilAndGasProperties | 
| Capitalized asset retirement obligation | 2,095us-gaap_CostsIncurredAssetRetirementObligationIncurred | 3,556us-gaap_CostsIncurredAssetRetirementObligationIncurred | 2,195us-gaap_CostsIncurredAssetRetirementObligationIncurred | 
| Total | 1,354,801gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities | 820,637gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities | 755,926gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities | 
| Diamondback Energy, Inc [Member] | |||
| Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] | |||
| Acquisition | 0us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 44,534us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 49,895us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 
| Development of proved undeveloped properties | 0us-gaap_CostsIncurredDevelopmentCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 6,369us-gaap_CostsIncurredDevelopmentCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 22,740us-gaap_CostsIncurredDevelopmentCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 
| Exploratory | 0us-gaap_CostsIncurredExplorationCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 17,491us-gaap_CostsIncurredExplorationCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 3,755us-gaap_CostsIncurredExplorationCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 
| Capitalized asset retirement obligation | 0us-gaap_CostsIncurredAssetRetirementObligationIncurred / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 50us-gaap_CostsIncurredAssetRetirementObligationIncurred / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 203us-gaap_CostsIncurredAssetRetirementObligationIncurred / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 
| Total | 0gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 68,444gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 76,593gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 
| Grizzly Oil Sands ULC [Member] | |||
| Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] | |||
| Acquisition | 1,230us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0us-gaap_CostsIncurredAcquisitionOfOilAndGasProperties / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 
| Development of proved undeveloped properties | 7,107us-gaap_CostsIncurredDevelopmentCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0us-gaap_CostsIncurredDevelopmentCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0us-gaap_CostsIncurredDevelopmentCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 
| Exploratory | 0us-gaap_CostsIncurredExplorationCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0us-gaap_CostsIncurredExplorationCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0us-gaap_CostsIncurredExplorationCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 
| Capitalized asset retirement obligation | 1,055us-gaap_CostsIncurredAssetRetirementObligationIncurred / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0us-gaap_CostsIncurredAssetRetirementObligationIncurred / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0us-gaap_CostsIncurredAssetRetirementObligationIncurred / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 
| Total | $ 9,392gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | $ 0gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | $ 0gpor_TotalCostsIncurredInOilAndGasPropertiesAcquisitionAndDevelopmentActivities / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 
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- Definition Costs incurred for the recompletion of oil and gas wells No definition available. 
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- Definition Total costs incurred in oil and gas properties acquisition and development activities No definition available. 
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- Definition Cost incurred, including capitalized costs and costs charged to expense, in acquisition of oil and gas properties. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of asset retirement obligations (ARO) costs incurred (whether capitalized or charged to expense) during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Development costs incurred, including capitalized costs and costs charged to expense, in oil and gas activities. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Exploration costs incurred, including capitalized costs and costs charged to expense, in oil and gas activities. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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