Retirement Plans And Postretirement Benefits (Retirement Plan Weighted Average Asset Allocations) (Details)
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12 Months Ended |
Dec. 31, 2014
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Fixed Income Securities [Member] |
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Defined Benefit Plan Disclosure [Line Items] |
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Weighted average target asset allocations |
100.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_FixedIncomeSecuritiesMember |
U.S. [Member] | Plan Assets [Member] |
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Defined Benefit Plan Disclosure [Line Items] |
|
Weighted average asset allocations |
100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = gti_PlanAssetsMember |
U.S. [Member] | Equity Securities [Member] |
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Defined Benefit Plan Disclosure [Line Items] |
|
Weighted average target asset allocations |
20.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_EquitySecuritiesMember / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember |
U.S. [Member] | Equity Securities [Member] | Plan Assets [Member] |
|
Defined Benefit Plan Disclosure [Line Items] |
|
Weighted average asset allocations |
20.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_EquitySecuritiesMember / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = gti_PlanAssetsMember |
U.S. [Member] | Fixed Income Securities [Member] |
|
Defined Benefit Plan Disclosure [Line Items] |
|
Weighted average target asset allocations |
80.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember |
U.S. [Member] | Fixed Income Securities [Member] | Plan Assets [Member] |
|
Defined Benefit Plan Disclosure [Line Items] |
|
Weighted average asset allocations |
80.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = gti_PlanAssetsMember |
Foreign [Member] | Plan Assets [Member] |
|
Defined Benefit Plan Disclosure [Line Items] |
|
Weighted average asset allocations |
100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_ForeignPensionPlansDefinedBenefitMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = gti_PlanAssetsMember |
Foreign [Member] | Equity Securities [Member] | Plan Assets [Member] |
|
Defined Benefit Plan Disclosure [Line Items] |
|
Weighted average asset allocations |
0.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_EquitySecuritiesMember / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_ForeignPensionPlansDefinedBenefitMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = gti_PlanAssetsMember |
Foreign [Member] | Fixed Income Securities [Member] | Plan Assets [Member] |
|
Defined Benefit Plan Disclosure [Line Items] |
|
Weighted average asset allocations |
100.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations / us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis = us-gaap_FixedIncomeSecuritiesMember / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_ForeignPensionPlansDefinedBenefitMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = gti_PlanAssetsMember |