Annual report pursuant to Section 13 and 15(d)

Supplemental Information On Oil And Gas Exploration And Production Activities (Capitalized Costs Related to Oil and Gas Producing Activities) (Details)

v2.4.1.9
Supplemental Information On Oil And Gas Exploration And Production Activities (Capitalized Costs Related to Oil and Gas Producing Activities) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Reserve Quantities [Line Items]    
Proven properties $ 2,457,616us-gaap_CapitalizedCostsProvedProperties $ 1,526,588us-gaap_CapitalizedCostsProvedProperties
Unproven properties 1,465,538us-gaap_CapitalizedCostsUnprovedProperties 950,590us-gaap_CapitalizedCostsUnprovedProperties
Capitalized costs, gross 3,923,154us-gaap_CapitalizedCostsOilAndGasProducingActivitiesGross 2,477,178us-gaap_CapitalizedCostsOilAndGasProducingActivitiesGross
Accumulated depreciation, depletion, amortization and impairment reserve (1,044,273)us-gaap_CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities (779,561)us-gaap_CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities
Net capitalized costs 2,878,881us-gaap_CapitalizedCostsOilAndGasProducingActivitiesNet 1,697,617us-gaap_CapitalizedCostsOilAndGasProducingActivitiesNet
Diamondback Energy, Inc [Member]    
Reserve Quantities [Line Items]    
Proven properties 0us-gaap_CapitalizedCostsProvedProperties
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
92,074us-gaap_CapitalizedCostsProvedProperties
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Unproven properties 0us-gaap_CapitalizedCostsUnprovedProperties
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
26,608us-gaap_CapitalizedCostsUnprovedProperties
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Capitalized costs, gross 0us-gaap_CapitalizedCostsOilAndGasProducingActivitiesGross
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
118,682us-gaap_CapitalizedCostsOilAndGasProducingActivitiesGross
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Accumulated depreciation, depletion, amortization and impairment reserve 0us-gaap_CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
(15,180)us-gaap_CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Net capitalized costs 0us-gaap_CapitalizedCostsOilAndGasProducingActivitiesNet
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
103,502us-gaap_CapitalizedCostsOilAndGasProducingActivitiesNet
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_DiamondbackEnergyIncMember
Grizzly Oil Sands ULC [Member]    
Reserve Quantities [Line Items]    
Proven properties 96,859us-gaap_CapitalizedCostsProvedProperties
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_CapitalizedCostsProvedProperties
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Unproven properties 103,160us-gaap_CapitalizedCostsUnprovedProperties
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_CapitalizedCostsUnprovedProperties
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Capitalized costs, gross 200,019us-gaap_CapitalizedCostsOilAndGasProducingActivitiesGross
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_CapitalizedCostsOilAndGasProducingActivitiesGross
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Accumulated depreciation, depletion, amortization and impairment reserve (1,248)us-gaap_CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
0us-gaap_CapitalizedCostsAccumulatedDepreciationDepletionAmortizationAndValuationAllowanceForRelatingToOilAndGasProducingActivities
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
Net capitalized costs $ 198,771us-gaap_CapitalizedCostsOilAndGasProducingActivitiesNet
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember
$ 0us-gaap_CapitalizedCostsOilAndGasProducingActivitiesNet
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= gpor_GrizzlyOilSandsUlcMember