Fair Value of Financial Instruments (Details) (USD $)
In Millions, unless otherwise specified |
Mar. 31, 2015
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Aug. 18, 2014
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Dec. 21, 2012
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Oct. 17, 2012
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Debt Instrument [Line Items] | ||||
Fair value of notes | $ 615.8us-gaap_DebtInstrumentFairValue | |||
October Notes [Member] | ||||
Debt Instrument [Line Items] | ||||
Unamortized discount |
2.8us-gaap_DebtInstrumentUnamortizedDiscount / us-gaap_DebtInstrumentAxis = gpor_OctoberNotesMember |
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December Notes [Member] | ||||
Debt Instrument [Line Items] | ||||
Unamortized premium |
0.4us-gaap_DebtInstrumentUnamortizedPremium / us-gaap_DebtInstrumentAxis = gpor_DecemberNotesMember |
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August Notes [Member] | ||||
Debt Instrument [Line Items] | ||||
Unamortized premium |
16.5us-gaap_DebtInstrumentUnamortizedPremium / us-gaap_DebtInstrumentAxis = gpor_AugustNotesMember |
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Senior Notes [Member] | ||||
Debt Instrument [Line Items] | ||||
Carrying value of debt |
614.1us-gaap_DebtLongtermAndShorttermCombinedAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |
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Unamortized discount |
3.7us-gaap_DebtInstrumentUnamortizedDiscount / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |
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Unamortized premium |
$ 18.0us-gaap_DebtInstrumentUnamortizedPremium / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |
$ 0.5us-gaap_DebtInstrumentUnamortizedPremium / us-gaap_LongtermDebtTypeAxis = us-gaap_SeniorNotesMember |
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- Definition
Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The amount of debt premium that was originally recognized at the issuance of the instrument that has yet to be amortized. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Represents the aggregate of total long-term debt, including current maturities and short-term debt. No definition available.
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