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Hedging Activities (Schedule Of Derivative Instruments) (Details) |  |  | 6 Months Ended
--- | --- | --- | ---
Jun. 30, 2013 | Dec. 31, 2012 | Jun. 30, 2012 July - December 2012 | Jun. 30, 2012 January - June 2013
Derivative [Line Items] |  |  |  |
Daily Volume (Bbls/day) |  |  | 3,000 | 1,000
Weighted Average Price | 113.20 | 109.73 |  |

X
- Definition Production volume per day in barrels under contract. + References No definition available. + Details
Name: | gpor_ProductionBarrelsPerDay
Namespace Prefix: | gpor_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
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: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant