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Subsequent Events (Details) (USD $) In Millions, unless otherwise specified | 0 Months Ended |
--- | --- | ---
Feb. 15, 2013 | Dec. 21, 2012 | Dec. 18, 2012 | Dec. 19, 2012 | Feb. 26, 2015
Utica Shale [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Purchase price commitment | $ 220.0 us-gaap_PaymentsToAcquireOilAndGasPropertyAndEquipment / us-gaap_BusinessAcquisitionAxis = gpor_UticaShaleMember | $ 70.0 us-gaap_PaymentsToAcquireOilAndGasPropertyAndEquipment / us-gaap_BusinessAcquisitionAxis = gpor_UticaShaleMember | $ 302.0 us-gaap_PaymentsToAcquireOilAndGasPropertyAndEquipment / us-gaap_BusinessAcquisitionAxis = gpor_UticaShaleMember | $ 372.0 us-gaap_PaymentsToAcquireOilAndGasPropertyAndEquipment / us-gaap_BusinessAcquisitionAxis = gpor_UticaShaleMember |
Subsequent Event [Member] | Swap [Member] | Oil [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional quantity |  |  |  |  | 1,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_EnergyAxis = us-gaap_OilReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Average fixed price |  |  |  |  | 62.25 us-gaap_DerivativeSwapTypeAverageFixedPrice / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_EnergyAxis = us-gaap_OilReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Subsequent Event [Member] | Natural Gas Fixed Swap, January 2016 Through December 2017 [Member] | Swap [Member] | Gas [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional quantity |  |  |  |  | 30,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NaturalGasFixedSwapTermOneMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Average fixed price |  |  |  |  | 3.40 us-gaap_DerivativeSwapTypeAverageFixedPrice / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NaturalGasFixedSwapTermOneMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Subsequent Event [Member] | Natural Gas Fixed Swap, Term Two [Member] | Swap [Member] | Gas [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional quantity |  |  |  |  | 80,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NaturalGasFixedSwapTermTwoMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Average fixed price |  |  |  |  | 3.45 us-gaap_DerivativeSwapTypeAverageFixedPrice / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NaturalGasFixedSwapTermTwoMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Subsequent Event [Member] | Natural Gas Fixed Swap, Term Three [Member] | Swap [Member] | Gas [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional quantity |  |  |  |  | 30,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NaturalGasFixedSwapTermThreeMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Average fixed price |  |  |  |  | 3.40 us-gaap_DerivativeSwapTypeAverageFixedPrice / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NaturalGasFixedSwapTermThreeMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Subsequent Event [Member] | Nature Gas Basis Swap, Term One [Member] | Swap [Member] | Gas [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional quantity |  |  |  |  | 30,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NatureGasBasisSwapTermOneMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Hedge differential |  |  |  |  | 0.02 gpor_DerivativeHedgeDifferential / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NatureGasBasisSwapTermOneMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Subsequent Event [Member] | Nature Gas Basis Swap, Term Two [Member] | Swap [Member] | Gas [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional quantity |  |  |  |  | 10,000 invest_DerivativeNonmonetaryNotionalAmount / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NatureGasBasisSwapTermTwoMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Hedge differential |  |  |  |  | 0.01 gpor_DerivativeHedgeDifferential / us-gaap_DerivativeByNatureAxis = us-gaap_SwapMember / us-gaap_DerivativeInstrumentRiskAxis = gpor_NatureGasBasisSwapTermTwoMember / us-gaap_EnergyAxis = us-gaap_NaturalGasReservesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember

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- Definition Derivative, Hedge Differential + References No definition available. + Details
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Balance Type: | na
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- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Details
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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
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Namespace Prefix: | us-gaap_
Data Type: | us-types:perUnitItemType
Balance Type: | na
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- Definition The cash outflow to purchase long lived physical asset for use in the normal oil and gas operations and to purchase mineral interests in oil and gas properties not intended for resale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
Name: | us-gaap_BusinessAcquisitionAxis=gpor_UticaShaleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
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