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Derivative Instruments - Narrative (Details) | 12 Months Ended
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Dec. 31, 2017 MMBTU $ / MMBTU
Derivative [Line Items] |
Derivative, extension option term | 12 months
Production delivered under fixed price swaps, percentage | 68.00%
Fixed Price Swap 2019 |
Derivative [Line Items] |
Daily volume (MMBtu/day) | MMBTU | 100,000
Weighted average price of derivative swap (usd per MMBtu or Bbls) | $ / MMBTU | 3.05

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- Definition Derivative, Extension Option Term + References No definition available. + Details
Name: | gpor_DerivativeExtensionOptionTerm
Namespace Prefix: | gpor_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Production Delivered Under Fixed Price Swaps, Percentage + References No definition available. + Details
Name: | gpor_ProductionDeliveredUnderFixedPriceSwapsPercentage
Namespace Prefix: | gpor_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Nominal energy measure used to calculate payments on a derivative instrument. + References No definition available. + Details
Name: | us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure
Namespace Prefix: | us-gaap_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | duration

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- Definition Average fixed price related to the group of price risk swap derivatives. + References No definition available. + Details
Name: | us-gaap_DerivativeSwapTypeAverageFixedPrice
Namespace Prefix: | us-gaap_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | gpor_PositionMaturityAxis=gpor_FixedPriceSwap2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |