XML 70 R96.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Supplemental Information On Oil And Gas Exploration And Production Activities (Changes in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves) (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Changes In Standardized Measure of Discontinued Future Net Cash Flows [Line Items] |  |  |
Sales and transfers of oil and gas produced, net of production costs | $ (530,098)us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts | $ (197,559)us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts | $ (194,893)us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts
Net changes in prices, production costs, and development costs | 97,716 gpor_NetChangesInPricesProductionCostsAndDevelopment | 65,573 gpor_NetChangesInPricesProductionCostsAndDevelopment | 108,941 gpor_NetChangesInPricesProductionCostsAndDevelopment
Acquisition of oil and gas reserves in place | 14,266 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace | 0 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace | 0 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace
Extensions and discoveries | 790,533 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts | 130,826 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts | 151,654 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts
Previously estimated development costs incurred during the period | 68,227 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod | 43,478 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod | 10,211 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod
Revisions of previous quantity estimates, less related production costs | (37,801)us-gaap_RevisionsOfPreviousQuantityEstimates | (3,591)us-gaap_RevisionsOfPreviousQuantityEstimates | (10,504)us-gaap_RevisionsOfPreviousQuantityEstimates
Sales of reserves in place | 0 us-gaap_DecreaseDueToSalesOfMineralsInPlace | 0 us-gaap_DecreaseDueToSalesOfMineralsInPlace | (214,867)us-gaap_DecreaseDueToSalesOfMineralsInPlace
Accretion of discount | 57,847 us-gaap_AccretionOfDiscount | 34,864 us-gaap_AccretionOfDiscount | 37,668 us-gaap_AccretionOfDiscount
Net changes in income taxes | (295,226)us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves | (30,239)us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves | 25,585 us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves
Change in production rates and other | 683,237 gpor_ChangeInProductionRatesAndOther | 186,473 gpor_ChangeInProductionRatesAndOther | 58,165 gpor_ChangeInProductionRatesAndOther
Total change in standardized measure of discounted future net cash flows | 848,701 us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease | 229,825 us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease | (28,040)us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease
Diamondback Energy, Inc [Member] |  |  |
Changes In Standardized Measure of Discontinued Future Net Cash Flows [Line Items] |  |  |
Sales and transfers of oil and gas produced, net of production costs | 0 us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (12,524)us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (11,601)us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Net changes in prices, production costs, and development costs | 0 gpor_NetChangesInPricesProductionCostsAndDevelopment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 3,312 gpor_NetChangesInPricesProductionCostsAndDevelopment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (14,596)gpor_NetChangesInPricesProductionCostsAndDevelopment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Acquisition of oil and gas reserves in place | 0 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 21,968 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 23,090 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Extensions and discoveries | 0 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 39,776 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 16,969 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Previously estimated development costs incurred during the period | 0 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 5,517 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 19,014 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Revisions of previous quantity estimates, less related production costs | 0 us-gaap_RevisionsOfPreviousQuantityEstimates / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (9,143)us-gaap_RevisionsOfPreviousQuantityEstimates / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (4,897)us-gaap_RevisionsOfPreviousQuantityEstimates / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Accretion of discount | 0 us-gaap_AccretionOfDiscount / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 4,175 us-gaap_AccretionOfDiscount / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 7,803 us-gaap_AccretionOfDiscount / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Net changes in income taxes | 0 us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (12,137)us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (26,866)us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Change in production rates and other | 0 gpor_ChangeInProductionRatesAndOther / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 2,862 gpor_ChangeInProductionRatesAndOther / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (8,358)gpor_ChangeInProductionRatesAndOther / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Total change in standardized measure of discounted future net cash flows | 0 us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (8,339)us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 558 us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Equity Method Investment, Change in Ownership | 0 gpor_EquityMethodInvestmentChangeinOwnership / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | (52,145)gpor_EquityMethodInvestmentChangeinOwnership / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember | 0 gpor_EquityMethodInvestmentChangeinOwnership / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_DiamondbackEnergyIncMember
Grizzly Oil Sands ULC [Member] |  |  |
Changes In Standardized Measure of Discontinued Future Net Cash Flows [Line Items] |  |  |
Sales and transfers of oil and gas produced, net of production costs | (4,664)us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Net changes in prices, production costs, and development costs | 76,518 gpor_NetChangesInPricesProductionCostsAndDevelopment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 gpor_NetChangesInPricesProductionCostsAndDevelopment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 gpor_NetChangesInPricesProductionCostsAndDevelopment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Acquisition of oil and gas reserves in place | 0 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_IncreaseDueToPurchasesOfMineralsInPlace / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Extensions and discoveries | 7,107 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Previously estimated development costs incurred during the period | 0 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Revisions of previous quantity estimates, less related production costs | (10,659)us-gaap_RevisionsOfPreviousQuantityEstimates / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_RevisionsOfPreviousQuantityEstimates / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_RevisionsOfPreviousQuantityEstimates / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Accretion of discount | 14,946 us-gaap_AccretionOfDiscount / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_AccretionOfDiscount / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_AccretionOfDiscount / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Net changes in income taxes | 9,162 us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Change in production rates and other | (25,738)gpor_ChangeInProductionRatesAndOther / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 gpor_ChangeInProductionRatesAndOther / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | 0 gpor_ChangeInProductionRatesAndOther / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember
Total change in standardized measure of discounted future net cash flows | $ (55,718)us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | $ 0 us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember | $ 0 us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = gpor_GrizzlyOilSandsUlcMember

X
- Definition Change in production rates and other + References No definition available. + Details
Name: | gpor_ChangeInProductionRatesAndOther
Namespace Prefix: | gpor_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | gpor_ChangesInStandardizedMeasureofDiscontinuedFutureNetCashFlowsLineItems
Namespace Prefix: | gpor_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Equity Method Investment, Change in Ownership + References No definition available. + Details
Name: | gpor_EquityMethodInvestmentChangeinOwnership
Namespace Prefix: | gpor_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Net change in sales and transfer prices and in production (lifting) costs related to future production and in the evaluation of the costs that will be required in future periods to make it possible to extract or process proved oil and gas reserves. + References No definition available. + Details
Name: | gpor_NetChangesInPricesProductionCostsAndDevelopment
Namespace Prefix: | gpor_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) in standardized measure of discounted future net cash flow as a result of passage of time. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_AccretionOfDiscount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of decrease in standardized measure of discounted future net cash flow as a result of sales of minerals in place. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_DecreaseDueToSalesOfMineralsInPlace
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase (decrease) in standardized measure of discounted future net cash flow as a result of extensions, discoveries and improved recovery of proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase (decrease) in standardized measure of discounted future net cash flow as a result of change in the estimated future income tax on future pretax net cash flows related to the entity's proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_IncreaseDecreaseInFutureIncomeTaxExpenseEstimatesOnFutureCashFlowsRelatedToProvedOilAndGasReserves
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase in standardized measure of discounted future net cash flow as a result of purchases of minerals in place. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_IncreaseDueToPurchasesOfMineralsInPlace
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of (increase) decrease in standardized measure of discounted future net cash flow as a result of previously estimated development costs incurred. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 31 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_PreviouslyEstimatedDevelopmentCostsIncurredDuringPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase (decrease) in standardized measure of discounted future net cash flow as a result of revisions of estimated quantity of oil and gas in proved reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_RevisionsOfPreviousQuantityEstimates
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of (increase) decrease in standardized measure of discounted future net cash flow as a result of sales and transfers of oil and gas produced. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of increase (decrease) in standardized measure of discounted future net cash flow relating to proved oil and gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 35 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447 + Details
Name: | us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

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

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