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Stock-Based Compensation (Summary Of Stock Option Plans By Exercise Price) (Details) (USD $)
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12 Months Ended |
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Dec. 31, 2014
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| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | |
| Number Outstanding (shares) | 5,000us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions |
| Number Exercisable (shares) | 5,000us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions |
| Exercise Price $9.07 [Member] | |
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | |
| Exercise Price (usd per share) |
$ 9.07gpor_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsExercisePrice / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = gpor_ExercisePriceNinePointZeroSevenMember |
| Number Outstanding (shares) |
5,000us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = gpor_ExercisePriceNinePointZeroSevenMember |
| Weighted Average Remaining Life (in years) | 0 years 8 months 8 days |
| Number Exercisable (shares) |
5,000us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions / us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis = gpor_ExercisePriceNinePointZeroSevenMember |
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- Definition
The price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices. No definition available.
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- Details
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- Definition
The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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