XML 46 R97.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Supplemental Information On Oil And Gas Exploration And Production Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Reserve Quantities [Line Items] |  |  |
Price per unit (usd per MMbls or MMcf) | 4.35 us-gaap_AverageSalesPrices | 3.67 us-gaap_AverageSalesPrices | 2.76 us-gaap_AverageSalesPrices
Future development costs estimated to be spend in 2015 | $ 221.0 gpor_FutureDevelopmentCostsEstimatedToBeSpentInYearOne |  |
Future development costs estimated to be spend in 2016 | 93.1 gpor_FutureDevelopmentCostsEstimatedToBeSpentInYearTwo |  |
Future development costs estimated to be spend in 2017 | $ 215.4 gpor_FutureDevelopmentCostsEstimatedToBeSpentInYearThree |  |
Diamondback Energy, Inc [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Ownership interest | 0.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 7.20%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 21.40%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Increase (decrease) in reserve during the period |  |  | 75,384,000 gpor_ProvedDevelopedAndUndevelopedReserveIncreaseDecreaseInReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Grizzly [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Ownership interest | 25.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyMember |  |
Utica Shale [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Increase (decrease) in reserve during the period | 786,347,000 gpor_ProvedDevelopedAndUndevelopedReserveIncreaseDecreaseInReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_UticaShaleMember | 166,832,000 gpor_ProvedDevelopedAndUndevelopedReserveIncreaseDecreaseInReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_UticaShaleMember | 40,049,000 gpor_ProvedDevelopedAndUndevelopedReserveIncreaseDecreaseInReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_UticaShaleMember
Southern Louisiana and Utica Fields [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Decrease in reserves relating to change in estimates |  |  | 15,837,000 gpor_ProvedDevelopedAndUndevelopedReserveRevisionsOfPreviousEstimatesEnergy / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_SouthernLouisianaandUticaFieldsMember
Rhino [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Increase (decrease) in reserve during the period | 12,019,000 gpor_ProvedDevelopedAndUndevelopedReserveIncreaseDecreaseInReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_RhinoMember |  |
Niobrara [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Increase (decrease) in reserve during the period |  |  | 1,748,000 gpor_ProvedDevelopedAndUndevelopedReserveIncreaseDecreaseInReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_NiobraraMember
Oil [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Price per unit (usd per MMbls or MMcf) | 94.99 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  |
Natural Gas Liquids [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Price per unit (usd per MMbls or MMcf) | 44.84 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember | 41.23 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |

X
- Definition Future development costs estimated to be spent in year one + References No definition available. + Details
Name: | gpor_FutureDevelopmentCostsEstimatedToBeSpentInYearOne
Namespace Prefix: | gpor_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Future development costs estimated to be spent in year three + References No definition available. + Details
Name: | gpor_FutureDevelopmentCostsEstimatedToBeSpentInYearThree
Namespace Prefix: | gpor_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Future development costs estimated to be spent in year two + References No definition available. + Details
Name: | gpor_FutureDevelopmentCostsEstimatedToBeSpentInYearTwo
Namespace Prefix: | gpor_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Proved Developed And Undeveloped Reserve Increase (Decrease) In Reserves + References No definition available. + Details
Name: | gpor_ProvedDevelopedAndUndevelopedReserveIncreaseDecreaseInReserves
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | duration

X
- Definition Proved Developed And Undeveloped Reserve, Revisions Of Previous Estimates, Energy + References No definition available. + Details
Name: | gpor_ProvedDevelopedAndUndevelopedReserveRevisionsOfPreviousEstimatesEnergy
Namespace Prefix: | gpor_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | duration

X
- Definition The revenues derived from sales of oil or gas in each geographic area during the reporting period divided by the number of barrels of oil produced or thousands of cubic feet of gas produced. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Industry Guide -Number 2 -Paragraph 3 -Subparagraph A + Details
Name: | us-gaap_AverageSalesPrices
Namespace Prefix: | us-gaap_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
Name: | us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_ReserveQuantitiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ReserveQuantitiesByTypeOfReserveAxis=us-gaap_NaturalGasLiquidsReservesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ReserveQuantitiesByTypeOfReserveAxis=us-gaap_OilReservesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gpor_DiamondbackEnergyIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gpor_GrizzlyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gpor_NiobraraMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gpor_RhinoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gpor_SouthernLouisianaandUticaFieldsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=gpor_UticaShaleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |