Quarterly report pursuant to Section 13 or 15(d)

Property And Equipment (Narrative) (Details)

v2.4.1.9
Property And Equipment (Narrative) (Details) (USD $)
 3 Months Ended 1 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Jan. 31, 2013
Dec. 31, 2014
Oct. 31, 2012
Oct. 11, 2012
May 07, 2012
Property, Plant and Equipment [Line Items]              
Cumulative capitalization of general and administrative costs incurred and capitalized to the full cost pool $ 79,900,000gpor_CumulativeCapitalizationOfGeneralAndAdministrativeCostsIncurredAndCapitalizedToFullCostPool            
Capitalized general and administrative costs 7,200,000gpor_CapitalizedGeneralAndAdministrativeCosts 6,300,000gpor_CapitalizedGeneralAndAdministrativeCosts          
Capitalized costs of oil and natural gas properties excluded from amortization 1,546,804,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative     1,465,538,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative      
Payment received from Diamondback (24,178,000)us-gaap_IncreaseDecreaseInAccountsReceivable 27,944,000us-gaap_IncreaseDecreaseInAccountsReceivable          
Diamondback [Member]              
Property, Plant and Equipment [Line Items]              
Investment (shares)           7,914,036us-gaap_InvestmentOwnedBalanceShares
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= gpor_DiamondbackMember 		 
Promissory note receivable           63,600,000us-gaap_NotesAndLoansReceivableNetCurrent
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= gpor_DiamondbackMember 		 
Ownership interest         21.40%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= gpor_DiamondbackMember 		  35.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= gpor_DiamondbackMember
Diamondback [Member] | Accounts Receivable - Related Party [Member]              
Property, Plant and Equipment [Line Items]              
Payment received from Diamondback     $ 18,600,000us-gaap_IncreaseDecreaseInAccountsReceivable
/ us-gaap_BalanceSheetLocationAxis
= gpor_AccountsReceivableRelatedPartyMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= gpor_DiamondbackMember 		       
Minimum [Member]              
Property, Plant and Equipment [Line Items]              
Expected number of years amortization will commence 3 years            
Maximum [Member]              
Property, Plant and Equipment [Line Items]              
Expected number of years amortization will commence 5 years