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Commitments - Schedule of Firm Sales Contracted with Third Parties (Details) | Dec. 31, 2017 MMBTU
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Commitments and Contingencies Disclosure [Abstract] |
2018 | 560,800
2019 | 659,000
2020 | 526,000
2021 | 372,000
2022 | 272,000
Thereafter | 240,000
Total | 2,629,800

X
- Definition Supply Commitment, Due After Fifth Year + References No definition available. + Details
Name: | gpor_SupplyCommitmentDueAfterFifthYear
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Supply Commitment, Due in Next Twelve Months + References No definition available. + Details
Name: | gpor_SupplyCommitmentDueinNextTwelveMonths
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Supply Commitment, Due in Year Five + References No definition available. + Details
Name: | gpor_SupplyCommitmentDueinYearFive
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Supply Commitment, Due in Year Four + References No definition available. + Details
Name: | gpor_SupplyCommitmentDueinYearFour
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Supply Commitment, Due in Year Three + References No definition available. + Details
Name: | gpor_SupplyCommitmentDueinYearThree
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Supply Commitment, Due in Year Two + References No definition available. + Details
Name: | gpor_SupplyCommitmentDueinYearTwo
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Supply Commitment, Total + References No definition available. + Details
Name: | gpor_SupplyCommitmentTotal
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration