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Property And Equipment (Summary Of Oil And Gas Properties Not Subject To Amortization) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	$ 1,546,804us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative	$ 1,465,538us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative
Colorado [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	5,088us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative / us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis = gpor_ColoradoPropertiesMember
Bakken [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	96us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative / us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis = gpor_BakkenPropertiesMember
Southern Louisiana [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	283us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative / us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis = gpor_SouthernLouisianaPropertiesMember
Ohio [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	1,541,292us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative / us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis = gpor_OhioPropertiesMember
Other [Member]
Capitalized Costs of Unproved Properties Excluded from Amortization [Line Items]
Total oil and gas properties not subject to amortization, total	$ 45us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative / us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis = gpor_OtherPropertiesMember

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- Definition

The sum of the capitalized costs incurred, as of the balance sheet date, of unproved properties excluded from amortization including acquisition costs, exploration costs, development costs, and production costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-10.(c)(7)(ii))

-URI http://asc.fasb.org/extlink&oid=50486907&loc=d3e511914-122862

+ Details

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