Annual report pursuant to Section 13 and 15(d)

Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheets (Details)

v2.4.1.9
Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheets (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Current assets:        
Cash and cash equivalents $ 142,340us-gaap_CashAndCashEquivalentsAtCarryingValue $ 458,956us-gaap_CashAndCashEquivalentsAtCarryingValue $ 167,088us-gaap_CashAndCashEquivalentsAtCarryingValue $ 93,897us-gaap_CashAndCashEquivalentsAtCarryingValue
Accounts receivable—oil and gas 103,858us-gaap_AccountsReceivableNetCurrent 58,824us-gaap_AccountsReceivableNetCurrent    
Accounts receivable-related parties 46us-gaap_DueFromRelatedPartiesCurrent 2,617us-gaap_DueFromRelatedPartiesCurrent    
Accounts receivable - intercompany   0us-gaap_DueFromAffiliateCurrent    
Prepaid expenses and other current assets 3,714us-gaap_PrepaidExpenseAndOtherAssetsCurrent 2,581us-gaap_PrepaidExpenseAndOtherAssetsCurrent    
Deferred tax asset 0us-gaap_DeferredTaxAssetsLiabilitiesNetCurrent 6,927us-gaap_DeferredTaxAssetsLiabilitiesNetCurrent    
Short-term derivative instruments 78,391us-gaap_DerivativeAssetsCurrent 324us-gaap_DerivativeAssetsCurrent    
Note receivable - related party 0us-gaap_NotesReceivableRelatedPartiesCurrent 875us-gaap_NotesReceivableRelatedPartiesCurrent    
Total current assets 328,349us-gaap_AssetsCurrent 531,104us-gaap_AssetsCurrent    
Property and equipment:        
Oil and natural gas properties 3,923,154us-gaap_OilAndGasPropertyFullCostMethodGross 2,477,178us-gaap_OilAndGasPropertyFullCostMethodGross    
Other property and equipment 18,344us-gaap_PropertyPlantAndEquipmentOther 11,131us-gaap_PropertyPlantAndEquipmentOther    
Accumulated depletion, depreciation, amortization and impairment (1,050,879)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment (784,717)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment    
Property and equipment, net 2,890,619us-gaap_PropertyPlantAndEquipmentNet 1,703,592us-gaap_PropertyPlantAndEquipmentNet    
Other assets:        
Equity investments 369,581us-gaap_EquityMethodInvestments 440,068us-gaap_EquityMethodInvestments    
Derivative instruments 24,448us-gaap_DerivativeInstrumentsAndHedgesNoncurrent 521us-gaap_DerivativeInstrumentsAndHedgesNoncurrent    
Other assets 19,396us-gaap_OtherAssetsNoncurrent 17,851us-gaap_OtherAssetsNoncurrent    
Total other assets 413,425gpor_TotalOtherAssets 458,440gpor_TotalOtherAssets    
Total assets 3,632,393us-gaap_Assets 2,693,136us-gaap_Assets    
Current liabilities:        
Accounts payable and accrued liabilities 371,410us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent 190,707us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent    
Accounts payable - intercompany 0us-gaap_DueToAffiliateCurrent 0us-gaap_DueToAffiliateCurrent    
Asset retirement obligation—current 75us-gaap_AssetRetirementObligationCurrent 795us-gaap_AssetRetirementObligationCurrent    
Short-term derivative instruments 0us-gaap_DerivativeLiabilitiesCurrent 12,280us-gaap_DerivativeLiabilitiesCurrent    
Deferred tax liability 27,070us-gaap_DeferredTaxLiabilitiesCurrent 0us-gaap_DeferredTaxLiabilitiesCurrent    
Current maturities of long-term debt 168us-gaap_LongTermDebtCurrent 159us-gaap_LongTermDebtCurrent    
Total current liabilities 398,723us-gaap_LiabilitiesCurrent 203,941us-gaap_LiabilitiesCurrent    
Long-term derivative instrument 0us-gaap_DerivativeLiabilitiesNoncurrent 11,366us-gaap_DerivativeLiabilitiesNoncurrent    
Asset retirement obligation—long-term 17,863us-gaap_AssetRetirementObligationsNoncurrent 14,288us-gaap_AssetRetirementObligationsNoncurrent    
Deferred tax liability 203,195us-gaap_DeferredTaxLiabilitiesGrossNoncurrent 114,275us-gaap_DeferredTaxLiabilitiesGrossNoncurrent    
Long-term debt, net of current maturities 716,316us-gaap_LongTermDebtNoncurrent 299,028us-gaap_LongTermDebtNoncurrent    
Total liabilities 1,336,097us-gaap_Liabilities 642,898us-gaap_Liabilities    
Stockholders’ equity:        
Common stock 856us-gaap_CommonStockValue 851us-gaap_CommonStockValue    
Paid-in capital 1,828,602us-gaap_AdditionalPaidInCapital 1,813,058us-gaap_AdditionalPaidInCapital    
Accumulated other comprehensive loss (26,675)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (9,781)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax    
Retained earnings (accumulated deficit) 493,513us-gaap_RetainedEarningsAccumulatedDeficit 246,110us-gaap_RetainedEarningsAccumulatedDeficit    
Total stockholders’ equity 2,296,296us-gaap_StockholdersEquity 2,050,238us-gaap_StockholdersEquity 1,126,408us-gaap_StockholdersEquity 632,350us-gaap_StockholdersEquity
Total liabilities and stockholders’ equity 3,632,393us-gaap_LiabilitiesAndStockholdersEquity 2,693,136us-gaap_LiabilitiesAndStockholdersEquity    
Parent [Member]        
Current assets:        
Cash and cash equivalents 141,535us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
451,431us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
165,293us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
93,124us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Accounts receivable—oil and gas 103,762us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
58,662us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Accounts receivable-related parties 46us-gaap_DueFromRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
2,617us-gaap_DueFromRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Accounts receivable - intercompany 45,222us-gaap_DueFromAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
21,379us-gaap_DueFromAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Prepaid expenses and other current assets 3,714us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
2,581us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Deferred tax asset   6,927us-gaap_DeferredTaxAssetsLiabilitiesNetCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Short-term derivative instruments 78,391us-gaap_DerivativeAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
324us-gaap_DerivativeAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Note receivable - related party   875us-gaap_NotesReceivableRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Total current assets 372,670us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
544,796us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Property and equipment:        
Oil and natural gas properties 3,887,874us-gaap_OilAndGasPropertyFullCostMethodGross
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
2,470,411us-gaap_OilAndGasPropertyFullCostMethodGross
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Other property and equipment 18,301us-gaap_PropertyPlantAndEquipmentOther
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
11,102us-gaap_PropertyPlantAndEquipmentOther
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Accumulated depletion, depreciation, amortization and impairment (1,050,855)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(784,695)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Property and equipment, net 2,855,320us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1,696,818us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Other assets:        
Equity investments 360,238us-gaap_EquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
432,727us-gaap_EquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Derivative instruments 24,448us-gaap_DerivativeInstrumentsAndHedgesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
521us-gaap_DerivativeInstrumentsAndHedgesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Other assets 19,396us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
17,851us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Total other assets 404,082gpor_TotalOtherAssets
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
451,099gpor_TotalOtherAssets
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Total assets 3,632,072us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
2,692,713us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Current liabilities:        
Accounts payable and accrued liabilities 371,089us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
190,284us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Accounts payable - intercompany 0us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Asset retirement obligation—current 75us-gaap_AssetRetirementObligationCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
795us-gaap_AssetRetirementObligationCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Short-term derivative instruments   12,280us-gaap_DerivativeLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Deferred tax liability 27,070us-gaap_DeferredTaxLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
     
Current maturities of long-term debt 168us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
159us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Total current liabilities 398,402us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
203,518us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Long-term derivative instrument   11,366us-gaap_DerivativeLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Asset retirement obligation—long-term 17,863us-gaap_AssetRetirementObligationsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
14,288us-gaap_AssetRetirementObligationsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Deferred tax liability 203,195us-gaap_DeferredTaxLiabilitiesGrossNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
114,275us-gaap_DeferredTaxLiabilitiesGrossNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Long-term debt, net of current maturities 716,316us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
299,028us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Total liabilities 1,335,776us-gaap_Liabilities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
642,475us-gaap_Liabilities
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Stockholders’ equity:        
Common stock 856us-gaap_CommonStockValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
851us-gaap_CommonStockValue
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Paid-in capital 1,828,602us-gaap_AdditionalPaidInCapital
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1,813,058us-gaap_AdditionalPaidInCapital
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Accumulated other comprehensive loss (26,675)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(9,781)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Retained earnings (accumulated deficit) 493,513us-gaap_RetainedEarningsAccumulatedDeficit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
246,110us-gaap_RetainedEarningsAccumulatedDeficit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Total stockholders’ equity 2,296,296us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
2,050,238us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Total liabilities and stockholders’ equity 3,632,072us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
2,692,713us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
   
Guarantor [Member]        
Current assets:        
Cash and cash equivalents 804us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
7,525us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
1,795us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
772us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
Accounts receivable—oil and gas 96us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
162us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Accounts receivable-related parties 0us-gaap_DueFromRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
0us-gaap_DueFromRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Accounts receivable - intercompany 27us-gaap_DueFromAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
27us-gaap_DueFromAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Prepaid expenses and other current assets   0us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Deferred tax asset   0us-gaap_DeferredTaxAssetsLiabilitiesNetCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Short-term derivative instruments   0us-gaap_DerivativeAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Note receivable - related party   0us-gaap_NotesReceivableRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Total current assets 927us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
7,714us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Property and equipment:        
Oil and natural gas properties 35,990us-gaap_OilAndGasPropertyFullCostMethodGross
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
7,340us-gaap_OilAndGasPropertyFullCostMethodGross
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Other property and equipment 43us-gaap_PropertyPlantAndEquipmentOther
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
29us-gaap_PropertyPlantAndEquipmentOther
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Accumulated depletion, depreciation, amortization and impairment (24)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
(22)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Property and equipment, net 36,009us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
7,347us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Other assets:        
Equity investments   0us-gaap_EquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Derivative instruments 0us-gaap_DerivativeInstrumentsAndHedgesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
0us-gaap_DerivativeInstrumentsAndHedgesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Other assets   0us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Total assets 36,936us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
15,061us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Current liabilities:        
Accounts payable and accrued liabilities 321us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
423us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Accounts payable - intercompany 45,143us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
21,296us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Asset retirement obligation—current   0us-gaap_AssetRetirementObligationCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Short-term derivative instruments   0us-gaap_DerivativeLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Current maturities of long-term debt   0us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Total current liabilities 45,464us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
21,719us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Long-term derivative instrument   0us-gaap_DerivativeLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Asset retirement obligation—long-term 0us-gaap_AssetRetirementObligationsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
0us-gaap_AssetRetirementObligationsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Deferred tax liability   0us-gaap_DeferredTaxLiabilitiesGrossNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Long-term debt, net of current maturities 0us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
0us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Total liabilities 45,464us-gaap_Liabilities
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
21,719us-gaap_Liabilities
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Stockholders’ equity:        
Common stock   0us-gaap_CommonStockValue
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Paid-in capital 322us-gaap_AdditionalPaidInCapital
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
322us-gaap_AdditionalPaidInCapital
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Accumulated other comprehensive loss   0us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Retained earnings (accumulated deficit) (8,850)us-gaap_RetainedEarningsAccumulatedDeficit
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
(6,980)us-gaap_RetainedEarningsAccumulatedDeficit
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Total stockholders’ equity (8,528)us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
(6,658)us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Total liabilities and stockholders’ equity 36,936us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
15,061us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_GuarantorSubsidiariesMember
   
Non-Guarantor [Member]        
Current assets:        
Cash and cash equivalents 1us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
1us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
Accounts receivable—oil and gas 0us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Accounts receivable-related parties 0us-gaap_DueFromRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_DueFromRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Accounts receivable - intercompany 0us-gaap_DueFromAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_DueFromAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Prepaid expenses and other current assets 0us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Deferred tax asset   0us-gaap_DeferredTaxAssetsLiabilitiesNetCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Short-term derivative instruments 0us-gaap_DerivativeAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_DerivativeAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Note receivable - related party   0us-gaap_NotesReceivableRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Total current assets 1us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
     
Property and equipment:        
Oil and natural gas properties   0us-gaap_OilAndGasPropertyFullCostMethodGross
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Other property and equipment   0us-gaap_PropertyPlantAndEquipmentOther
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Accumulated depletion, depreciation, amortization and impairment   0us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Property and equipment, net   0us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Other assets:        
Equity investments 180,217us-gaap_EquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
191,473us-gaap_EquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Derivative instruments 0us-gaap_DerivativeInstrumentsAndHedgesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_DerivativeInstrumentsAndHedgesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Other assets   0us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Total other assets 180,217gpor_TotalOtherAssets
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
191,473gpor_TotalOtherAssets
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Total assets 180,218us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
191,473us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Current liabilities:        
Accounts payable and accrued liabilities   0us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Accounts payable - intercompany 106us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
110us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Asset retirement obligation—current   0us-gaap_AssetRetirementObligationCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Short-term derivative instruments   0us-gaap_DerivativeLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Current maturities of long-term debt   0us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Total current liabilities 106us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
110us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Long-term derivative instrument   0us-gaap_DerivativeLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Asset retirement obligation—long-term 0us-gaap_AssetRetirementObligationsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_AssetRetirementObligationsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Deferred tax liability   0us-gaap_DeferredTaxLiabilitiesGrossNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Long-term debt, net of current maturities 0us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
0us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Total liabilities 106us-gaap_Liabilities
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
110us-gaap_Liabilities
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Stockholders’ equity:        
Common stock   0us-gaap_CommonStockValue
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Paid-in capital 227,079us-gaap_AdditionalPaidInCapital
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
208,277us-gaap_AdditionalPaidInCapital
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Accumulated other comprehensive loss (26,675)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
(9,781)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Retained earnings (accumulated deficit) (20,292)us-gaap_RetainedEarningsAccumulatedDeficit
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
(7,133)us-gaap_RetainedEarningsAccumulatedDeficit
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Total stockholders’ equity 180,112us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
191,363us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Total liabilities and stockholders’ equity 180,218us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
191,473us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_NonGuarantorSubsidiariesMember
   
Eliminations [Member]        
Current assets:        
Cash and cash equivalents 0us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
0us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
0us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
0us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
Accounts receivable—oil and gas   0us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Accounts receivable-related parties 0us-gaap_DueFromRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
0us-gaap_DueFromRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Accounts receivable - intercompany (45,249)us-gaap_DueFromAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(21,406)us-gaap_DueFromAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Prepaid expenses and other current assets   0us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Deferred tax asset   0us-gaap_DeferredTaxAssetsLiabilitiesNetCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Short-term derivative instruments   0us-gaap_DerivativeAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Note receivable - related party   0us-gaap_NotesReceivableRelatedPartiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Total current assets (45,249)us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(21,406)us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Property and equipment:        
Oil and natural gas properties (710)us-gaap_OilAndGasPropertyFullCostMethodGross
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(573)us-gaap_OilAndGasPropertyFullCostMethodGross
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Other property and equipment   0us-gaap_PropertyPlantAndEquipmentOther
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Accumulated depletion, depreciation, amortization and impairment   0us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Property and equipment, net (710)us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(573)us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Other assets:        
Equity investments (170,874)us-gaap_EquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(184,132)us-gaap_EquityMethodInvestments
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Derivative instruments 0us-gaap_DerivativeInstrumentsAndHedgesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
0us-gaap_DerivativeInstrumentsAndHedgesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Other assets   0us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Total other assets (170,874)gpor_TotalOtherAssets
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(184,132)gpor_TotalOtherAssets
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Total assets (216,833)us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(206,111)us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Current liabilities:        
Accounts payable and accrued liabilities   0us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Accounts payable - intercompany (45,249)us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(21,406)us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Asset retirement obligation—current   0us-gaap_AssetRetirementObligationCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Short-term derivative instruments   0us-gaap_DerivativeLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Current maturities of long-term debt   0us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Total current liabilities (45,249)us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(21,406)us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Long-term derivative instrument   0us-gaap_DerivativeLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Asset retirement obligation—long-term 0us-gaap_AssetRetirementObligationsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
0us-gaap_AssetRetirementObligationsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Deferred tax liability   0us-gaap_DeferredTaxLiabilitiesGrossNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Long-term debt, net of current maturities 0us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
0us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Total liabilities (45,249)us-gaap_Liabilities
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(21,406)us-gaap_Liabilities
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Stockholders’ equity:        
Common stock   0us-gaap_CommonStockValue
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Paid-in capital (227,401)us-gaap_AdditionalPaidInCapital
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(208,599)us-gaap_AdditionalPaidInCapital
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Accumulated other comprehensive loss 26,675us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
9,781us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Retained earnings (accumulated deficit) 29,142us-gaap_RetainedEarningsAccumulatedDeficit
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
14,113us-gaap_RetainedEarningsAccumulatedDeficit
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Total stockholders’ equity (171,584)us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
(184,705)us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
   
Total liabilities and stockholders’ equity $ (216,833)us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember
$ (206,111)us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_ConsolidationEliminationsMember