Annual report pursuant to Section 13 and 15(d)

Commitments (Details)

v2.4.1.9
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   $ 3,097,000gpor_PluggingAndAbandonmentEscrowAccount $ 3,105,000gpor_PluggingAndAbandonmentEscrowAccount    
Maximum annual contributions per employee (401K Plan)   100.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent      
Cost recognized on defined contribution plan   800,000us-gaap_DefinedContributionPlanCostRecognized 600,000us-gaap_DefinedContributionPlanCostRecognized 400,000us-gaap_DefinedContributionPlanCostRecognized  
Employment Agreement, Term 3 years        
Employment Agreement, Subsequent Extension 1 year        
Employment Agreement, Notice Period Allowed For Termination 90 days        
Other Commitment   196,650,000us-gaap_OtherCommitment      
Sales Commitment, Volume   218,000gpor_SalesCommitmentVolume      
Expiration Year One [Member]          
Commitments [Line Items]          
Sales Commitment, Volume   33,000gpor_SalesCommitmentVolume
/ us-gaap_SupplyCommitmentAxis
= gpor_ExpirationYearOneMember 		     
Expiration Year Two [Member]          
Commitments [Line Items]          
Sales Commitment, Volume   5,000gpor_SalesCommitmentVolume
/ us-gaap_SupplyCommitmentAxis
= gpor_ExpirationYearTwoMember 		     
Expiration Year Three [Member]          
Commitments [Line Items]          
Sales Commitment, Volume   30,000gpor_SalesCommitmentVolume
/ us-gaap_SupplyCommitmentAxis
= gpor_ExpirationYearThreeMember 		     
Expiration Year Four [Member]          
Commitments [Line Items]          
Sales Commitment, Volume   50,000gpor_SalesCommitmentVolume
/ us-gaap_SupplyCommitmentAxis
= gpor_ExpirationYearFourMember 		     
Expiration Year Five [Member]          
Commitments [Line Items]          
Sales Commitment, Volume   50,000gpor_SalesCommitmentVolume
/ us-gaap_SupplyCommitmentAxis
= gpor_ExpirationYearFiveMember 		     
Expiration Year Eight [Member]          
Commitments [Line Items]          
Sales Commitment, Volume   50,000gpor_SalesCommitmentVolume
/ us-gaap_SupplyCommitmentAxis
= gpor_ExpirationYearEightMember 		     
Chief Executive Officer [Member]          
Commitments [Line Items]          
Other Commitment   600,000us-gaap_OtherCommitment
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ChiefExecutiveOfficerMember 		     
Executive Officer [Member]          
Commitments [Line Items]          
Other Commitment   900,000us-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         18,000gpor_PaymentsHeldForRestrictedCash
/ us-gaap_BusinessAcquisitionAxis
= gpor_WcbbMember
Significant Plugging Commitment Minimum Number Of Wells To Be Plugged         20gpor_SignificantPluggingCommitmentMinimumNumberOfWellsToBePlugged
/ us-gaap_BusinessAcquisitionAxis
= gpor_WcbbMember
Tenure Of Minimum Wells To Be Plugged         20 years
Number Of Wells Plugged   450gpor_NumberOfWellsPlugged
/ us-gaap_BusinessAcquisitionAxis
= gpor_WcbbMember 		     
Muskie Proppant LLC [Member]          
Commitments [Line Items]          
Accrued damages for non-utilization of supply contract obligations   $ 300,000gpor_LongtermPurchaseCommitmentAccruedDamagesAmount
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_MuskieProppantLLCMember