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Commitments (Details) (USD $) | 0 Months Ended | 12 Months Ended | 0 Months Ended
--- | --- | --- | ---
Nov. 02, 2012 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Mar. 11, 1997 wells
Commitments [Line Items] |  |  |  |  |
Plugging And Abandonment Escrow Account |  | $ 3,097,000 gpor_PluggingAndAbandonmentEscrowAccount | $ 3,105,000 gpor_PluggingAndAbandonmentEscrowAccount |  |
Maximum annual contributions per employee (401K Plan) |  | 100.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent |  |  |
Cost recognized on defined contribution plan |  | 800,000 us-gaap_DefinedContributionPlanCostRecognized | 600,000 us-gaap_DefinedContributionPlanCostRecognized | 400,000 us-gaap_DefinedContributionPlanCostRecognized |
Employment Agreement, Term | 3 years |  |  |  |
Employment Agreement, Subsequent Extension | 1 year |  |  |  |
Employment Agreement, Notice Period Allowed For Termination | 90 days |  |  |  |
Other Commitment |  | 196,650,000 us-gaap_OtherCommitment |  |  |
Sales Commitment, Volume |  | 218,000 gpor_SalesCommitmentVolume |  |  |
Expiration Year One [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Sales Commitment, Volume |  | 33,000 gpor_SalesCommitmentVolume / us-gaap_SupplyCommitmentAxis = gpor_ExpirationYearOneMember |  |  |
Expiration Year Two [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Sales Commitment, Volume |  | 5,000 gpor_SalesCommitmentVolume / us-gaap_SupplyCommitmentAxis = gpor_ExpirationYearTwoMember |  |  |
Expiration Year Three [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Sales Commitment, Volume |  | 30,000 gpor_SalesCommitmentVolume / us-gaap_SupplyCommitmentAxis = gpor_ExpirationYearThreeMember |  |  |
Expiration Year Four [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Sales Commitment, Volume |  | 50,000 gpor_SalesCommitmentVolume / us-gaap_SupplyCommitmentAxis = gpor_ExpirationYearFourMember |  |  |
Expiration Year Five [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Sales Commitment, Volume |  | 50,000 gpor_SalesCommitmentVolume / us-gaap_SupplyCommitmentAxis = gpor_ExpirationYearFiveMember |  |  |
Expiration Year Eight [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Sales Commitment, Volume |  | 50,000 gpor_SalesCommitmentVolume / us-gaap_SupplyCommitmentAxis = gpor_ExpirationYearEightMember |  |  |
Chief Executive Officer [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Other Commitment |  | 600,000 us-gaap_OtherCommitment / us-gaap_TitleOfIndividualAxis = us-gaap_ChiefExecutiveOfficerMember |  |  |
Executive Officer [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Other Commitment |  | 900,000 us-gaap_OtherCommitment / us-gaap_TitleOfIndividualAxis = us-gaap_ExecutiveOfficerMember |  |  |
Minimum [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Minimum matching employer contribution for 401K |  | 3.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |
WCBB [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Purchasing Remaining Percent Interest In Oil And Gas Property |  |  |  |  | 50.00%gpor_PurchasingRemainingPercentInterestInOilAndGasProperty / us-gaap_BusinessAcquisitionAxis = gpor_WcbbMember
Payments Held For Restricted Cash |  |  |  |  | 18,000 gpor_PaymentsHeldForRestrictedCash / us-gaap_BusinessAcquisitionAxis = gpor_WcbbMember
Significant Plugging Commitment Minimum Number Of Wells To Be Plugged |  |  |  |  | 20 gpor_SignificantPluggingCommitmentMinimumNumberOfWellsToBePlugged / us-gaap_BusinessAcquisitionAxis = gpor_WcbbMember
Tenure Of Minimum Wells To Be Plugged |  |  |  |  | 20 years
Number Of Wells Plugged |  | 450 gpor_NumberOfWellsPlugged / us-gaap_BusinessAcquisitionAxis = gpor_WcbbMember |  |  |
Muskie Proppant LLC [Member] |  |  |  |  |
Commitments [Line Items] |  |  |  |  |
Accrued damages for non-utilization of supply contract obligations |  | $ 300,000 gpor_LongtermPurchaseCommitmentAccruedDamagesAmount / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_MuskieProppantLLCMember |  |  |

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- Definition Employment Agreement, Notice Period Allowed For Termination + References No definition available. + Details
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- Definition Number Of Wells Plugged + References No definition available. + Details
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- Definition payments to plugging and abandonment escrow account. + References No definition available. + Details
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- Definition Plugging And Abandonment Escrow Account + References No definition available. + Details
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- Definition The amount of the cost recognized during the period for defined contribution plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942 + Details
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- Definition Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions. + References No definition available. + Details
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