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Management Compensation And Incentive Plans (Narrative) (Details) (USD $) | 12 Months Ended | 1 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Jan. 30, 2012 anniversary | Dec. 30, 2014 employee | Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Aggregate number of shares authorized under the plans |  | 23,300,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized |  |  |  |
Stock-based compensation expense | $ 5,577,000 us-gaap_AllocatedShareBasedCompensationExpense | $ 7,700,000 us-gaap_AllocatedShareBasedCompensationExpense | $ 9,600,000 us-gaap_AllocatedShareBasedCompensationExpense |  |  |
Stock-based compensation | 5,577,000 us-gaap_ShareBasedCompensation | 8,035,000 us-gaap_ShareBasedCompensation | 9,601,000 us-gaap_ShareBasedCompensation |  |  |
Compensation expense related to non-vested restricted stock and stock options not yet recognized |  | 12,300,000 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized |  |  |  |
Compensation cost related to non-vested restricted stock, performance shares and stock options not yet recognized, weighted average life, in years | 1 year 11 months 16 days |  |  |  |  |
Range of exercise prices, lower range | $ 4.24 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit |  |  |  |  |
Range of exercise prices, upper range | $ 22.57 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit |  |  |  |  |
Dividend assumption | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate |  |  |  |  |
Intrinsic value of options exercised | 500,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue |  |  |  |  |
Weighted average remaining contractual life, years | 7 years 9 months 18 days |  |  |  |  |
Weighted average remaining vesting period, years | 1 year 6 months |  |  |  |  |
Options vested and expected to vest | 1,601,124 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber |  |  |  |  |
Weighted-average contractual life, years | 6 years 7 months 21 days |  |  |  |  |
Aggregate intrinsic value | 400,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue |  |  |  |  |
Directors, Officers And Employees [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of Shares, Granted |  | 1,466,919 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_TitleOfIndividualAxis = us-gaap_BoardOfDirectorsChairmanMember |  |  |  |
Weighted-average fair value of the options granted | $ 5.82 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_TitleOfIndividualAxis = us-gaap_BoardOfDirectorsChairmanMember | $ 11.53 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_TitleOfIndividualAxis = us-gaap_BoardOfDirectorsChairmanMember | $ 9.82 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_TitleOfIndividualAxis = us-gaap_BoardOfDirectorsChairmanMember |  |  |
Shares granted and expected to vest in particular period | 519,286 gti_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExpectedToVestInParticularPeriod / us-gaap_TitleOfIndividualAxis = us-gaap_BoardOfDirectorsChairmanMember |  |  |  |  |
Restricted stock and performance shares vest over period Year/month | 3 years |  |  |  |  |
Option Pricing Model [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of Shares, Granted | 671,939 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_TitleOfIndividualAxis = gti_OptionPricingModelMember | 348,106 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_TitleOfIndividualAxis = gti_OptionPricingModelMember | 441,700 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_TitleOfIndividualAxis = gti_OptionPricingModelMember |  |  |
Incentive Compensation Plan [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Accrued liability for incentive compensation plans | 0 gti_ShareBasedCompensationArrangementByShareBasedPaymentAwardAccruedLiabilityIncludedInCompensationPlans / us-gaap_TitleOfIndividualAxis = gti_IncentiveCompensationPlanMember | 400,000 gti_ShareBasedCompensationArrangementByShareBasedPaymentAwardAccruedLiabilityIncludedInCompensationPlans / us-gaap_TitleOfIndividualAxis = gti_IncentiveCompensationPlanMember |  |  |  |
Selling And Administrative Expense [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Stock-based compensation expense | 4,800,000 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = gti_SellingAndAdministrativeExpensesMember | 6,900,000 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = gti_SellingAndAdministrativeExpensesMember | 8,700,000 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_IncomeStatementLocationAxis = gti_SellingAndAdministrativeExpensesMember |  |  |
2011 Long-Term Incentive Plan [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of Shares, Granted |  |  |  | 526,900 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_PlanNameAxis = gti_TwoThousandAndElevenLongTermIncentivePlanMember |  |
Exercise price of stock option granted |  |  |  | $ 4.24 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_PlanNameAxis = gti_TwoThousandAndElevenLongTermIncentivePlanMember |  |
Grant Date Anniversaries |  |  |  | 3 gti_GrantDateAnniversaries / us-gaap_PlanNameAxis = gti_TwoThousandAndElevenLongTermIncentivePlanMember |  |
Expiration years from the grant date |  |  |  | 10 years |  |
Stock Options [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of Shares, Granted | 671,939 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |  |  |
Exercise price of stock option granted | $ 5.82 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |  |  |
Dividend assumption |  | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Restricted Stock And Performance Shares [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 1,466,919 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = gti_RestrictedStockAndPerformanceSharesMember |  |  |  |  |
Range of exercise prices, lower range | $ 4.24 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit / us-gaap_AwardTypeAxis = gti_RestrictedStockAndPerformanceSharesMember |  |  |  |  |
Range of exercise prices, upper range | $ 11.90 us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit / us-gaap_AwardTypeAxis = gti_RestrictedStockAndPerformanceSharesMember |  |  |  |  |
Shares granted and expected to vest in particular period | 200,000 gti_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExpectedToVestInParticularPeriod / us-gaap_AwardTypeAxis = gti_RestrictedStockAndPerformanceSharesMember |  |  |  |  |
Restricted stock and performance shares vest over period Year/month | 1 year |  |  |  |  |
Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted-average fair value of the options granted |  | $ 11.16 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |  |  |
Restricted Stock Units (RSUs) [Member] | 2011 Long-Term Incentive Plan [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of Shares, Granted |  |  |  | 395,186 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = gti_TwoThousandAndElevenLongTermIncentivePlanMember |  |
Grant Date Anniversaries |  |  |  | 3 gti_GrantDateAnniversaries / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember / us-gaap_PlanNameAxis = gti_TwoThousandAndElevenLongTermIncentivePlanMember |  |
Restricted Stock [Member] | Equity Recognition Program [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period |  |  |  |  | 195,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = gti_EquityRecognitionProgramMember |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Number of Directors Granted Units |  |  |  |  | 45 gti_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsNumberofDirectorsGrantedUnits / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = gti_EquityRecognitionProgramMember |
Share-based Compensation by Share-based Payment Award, Annual Vesting Percent |  |  |  |  | 100.00%gti_SharebasedCompensationbySharebasedPaymentAwardAnnualVestingPercent / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember / us-gaap_PlanNameAxis = gti_EquityRecognitionProgramMember |
Performance Shares [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted-average fair value of the options granted | $ 5.19 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |  |  |
Shares granted and expected to vest in particular period | 747,633 gti_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodExpectedToVestInParticularPeriod / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember |  |  |  |  |
Restricted stock and performance shares vest over period Year/month | 39 months |  |  |  |  |
Performance Shares [Member] | 2011 Long-Term Incentive Plan [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of Shares, Granted |  |  | 1,317,266 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember / us-gaap_PlanNameAxis = gti_TwoThousandAndElevenLongTermIncentivePlanMember |  |  |
Scenario, Forecast [Member] |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Stock-based compensation expense |  |  |  |  |  | $ 5,600,000 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_StatementScenarioAxis = us-gaap_ScenarioForecastMember

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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Net number of share options (or share units) granted during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options. + References No definition available. + Details
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- Definition The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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