Annual report pursuant to Section 13 and 15(d)

Supplemental Information On Oil And Gas Exploration And Production Activities (Results of Operations for Producing Activities) (Details)

v2.4.1.9
Supplemental Information On Oil And Gas Exploration And Production Activities (Results of Operations for Producing Activities) (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Results of Operations for Oil and Gas Producing Activities [Line Items]      
Revenues $ 670,762,000us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities $ 262,225,000us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities $ 248,601,000us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities
Production costs (140,664,000)us-gaap_ResultsOfOperationsProductionOrLiftingCosts (64,666,000)us-gaap_ResultsOfOperationsProductionOrLiftingCosts (53,708,000)us-gaap_ResultsOfOperationsProductionOrLiftingCosts
Depletion (263,946,000)us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions (118,118,000)us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions (90,230,000)us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions
Results of operations, before income taxes 266,152,000us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes 79,441,000us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes 104,663,000us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes
Current 0gpor_ResultsOfOperationsIncomeTaxExpenseCurrent 0gpor_ResultsOfOperationsIncomeTaxExpenseCurrent 730,000gpor_ResultsOfOperationsIncomeTaxExpenseCurrent
Deferred 96,061,000gpor_ResultsOfOperationsIncomeTaxExpenseDeferred 49,447,000gpor_ResultsOfOperationsIncomeTaxExpenseDeferred 25,633,000gpor_ResultsOfOperationsIncomeTaxExpenseDeferred
Income tax expense 96,061,000us-gaap_ResultsOfOperationsIncomeTaxExpense 49,447,000us-gaap_ResultsOfOperationsIncomeTaxExpense 26,363,000us-gaap_ResultsOfOperationsIncomeTaxExpense
Results of operations from producing activities 170,091,000us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts 29,994,000us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts 78,300,000us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts
Depletion per MCF of Gas Equivalent 3.01gpor_DepletionperMCFofGasEquivalent 4.78gpor_DepletionperMCFofGasEquivalent 5.85gpor_DepletionperMCFofGasEquivalent
Diamondback Energy, Inc [Member]      
Results of Operations for Oil and Gas Producing Activities [Line Items]      
Revenues 0us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
14,976,000us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
16,042,000us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Production costs 0us-gaap_ResultsOfOperationsProductionOrLiftingCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
(2,518,000)us-gaap_ResultsOfOperationsProductionOrLiftingCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
(4,474,000)us-gaap_ResultsOfOperationsProductionOrLiftingCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Depletion 0us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
(4,754,000)us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
(5,515,000)us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Results of operations, before income taxes 0us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
7,704,000us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
6,053,000us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Income tax expense 0us-gaap_ResultsOfOperationsIncomeTaxExpense
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
2,286,000us-gaap_ResultsOfOperationsIncomeTaxExpense
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
2,158,000us-gaap_ResultsOfOperationsIncomeTaxExpense
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Results of operations from producing activities 0us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
5,418,000us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
3,895,000us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Grizzly Oil Sands ULC [Member]      
Results of Operations for Oil and Gas Producing Activities [Line Items]      
Revenues 5,449,000us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsRevenueFromOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Production costs (10,113,000)us-gaap_ResultsOfOperationsProductionOrLiftingCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsProductionOrLiftingCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsProductionOrLiftingCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Depletion (1,195,000)us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsDepreciationDepletionAndAmortizationAndValuationProvisions
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Results of operations, before income taxes (5,859,000)us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsIncomeBeforeIncomeTaxes
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Income tax expense 0us-gaap_ResultsOfOperationsIncomeTaxExpense
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsIncomeTaxExpense
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_ResultsOfOperationsIncomeTaxExpense
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Results of operations from producing activities $ (5,859,000)us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
$ 0us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
$ 0us-gaap_ResultsOfOperationsOilAndGasProducingActivitiesNetIncomeExcludingCorporateOverheadAndInterestCosts
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember