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Derivative Instruments (Narrative) (Details) - 2019	3 Months Ended
	Mar. 31, 2018 MMBTU $ / MMBTU
Derivative [Line Items]
Daily volume (in MMBtu) | MMBTU	100,000
Weighted average price (in usd per MMBtu or Bbl) | $ / MMBTU	3.05

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

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- Definition

Nominal energy measure used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure
Namespace Prefix:	us-gaap_
Data Type:	num:energyItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Average fixed price related to the group of price risk swap derivatives.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeSwapTypeAverageFixedPrice
Namespace Prefix:	us-gaap_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

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- Details

Name:	gpor_PositionMaturityAxis=gpor_FixedPriceSwap2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: