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v2.4.1.9

Rationalizations Rollforward of Rationalization Liability (Details) (USD $) | 3 Months Ended | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | $ 11,625,000 us-gaap_RestructuringAndRelatedCostIncurredCost | $ 20,156,000 us-gaap_RestructuringAndRelatedCostIncurredCost | $ 0 us-gaap_RestructuringAndRelatedCostIncurredCost
Impairment of long-lived assets and goodwill | 75,700,000 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse | 197,220,000 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse | 0 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse | 0 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse
Rationalization Plan [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 184,378,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 65,701,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Impairment of long-lived assets and goodwill |  | 121,570,000 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |  |
Rationalization Plan [Member] | Cost of Sales [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 26,037,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 28,326,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Inventory Loss |  | 14,672,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 8,782,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Fixed Asset Write-offs and Other |  | 6,830,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 8,378,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Rationalization Plan [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 608,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |  |
Incurred Cost |  | 725,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 59,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Rationalization Plan [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 626,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 810,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Rationalization Plan [Member] | Research and Development Expense [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 2,312,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |  |
Rationalization Plan [Member] | Employee Severance [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 10,998,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 19,346,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Rationalization Plan [Member] | Industrial Materials [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 34,499,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 60,257,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Rationalization Plan [Member] | Industrial Materials [Member] | Cost of Sales [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 22,388,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 28,326,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Inventory Loss |  | 961,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 7,886,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Fixed Asset Write-offs and Other |  | 5,552,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 6,104,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Rationalization Plan [Member] | Industrial Materials [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |  |
Incurred Cost |  | 89,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 59,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Rationalization Plan [Member] | Industrial Materials [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 469,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 810,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Rationalization Plan [Member] | Industrial Materials [Member] | Research and Development Expense [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |  |
Rationalization Plan [Member] | Industrial Materials [Member] | Employee Severance [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 5,040,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 17,072,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Rationalization Plan [Member] | Engineered Solutions [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 143,588,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 3,628,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Impairment of long-lived assets and goodwill |  | 121,570,000 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |  |
Rationalization Plan [Member] | Engineered Solutions [Member] | Cost of Sales [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 3,649,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Inventory Loss |  | 13,711,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 896,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Fixed Asset Write-offs and Other |  | 1,278,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 2,274,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Rationalization Plan [Member] | Engineered Solutions [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |  |
Incurred Cost |  | 121,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Rationalization Plan [Member] | Engineered Solutions [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 146,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Rationalization Plan [Member] | Engineered Solutions [Member] | Research and Development Expense [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |  |
Rationalization Plan [Member] | Engineered Solutions [Member] | Employee Severance [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 3,113,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 458,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Rationalization Plan [Member] | Corporate and Other [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 6,291,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 1,816,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Impairment of long-lived assets and goodwill |  | 0 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |  |
Rationalization Plan [Member] | Corporate and Other [Member] | Cost of Sales [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Inventory Loss |  | 0 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Fixed Asset Write-offs and Other |  | 0 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Rationalization Plan [Member] | Corporate and Other [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 608,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |  |
Incurred Cost |  | 515,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Rationalization Plan [Member] | Corporate and Other [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 11,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Rationalization Plan [Member] | Corporate and Other [Member] | Research and Development Expense [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 2,312,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |  |
Rationalization Plan [Member] | Corporate and Other [Member] | Employee Severance [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 2,845,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 1,816,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2013 Rationalization Initiatives [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 23,200,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 28,300,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
Incurred Cost |  | 31,231,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 65,701,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
2013 Rationalization Initiatives [Member] | Cost of Sales [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 23,215,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 28,326,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
Inventory Loss |  | 1,446,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 8,782,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
Fixed Asset Write-offs and Other |  | 5,607,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 8,378,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
2013 Rationalization Initiatives [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 89,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 59,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
2013 Rationalization Initiatives [Member] | Employee Severance [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  |  | 20,200,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
2013 Rationalization Initiatives [Member] | Employee Severance [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 405,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 19,346,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
2013 Rationalization Initiatives [Member] | Special Termination Benefits [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 900,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |  |
2013 Rationalization Initiatives [Member] | Special Termination Benefits [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 469,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 810,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
2013 Rationalization Initiatives [Member] | Industrial Materials [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 29,714,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 60,257,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2013 Rationalization Initiatives [Member] | Industrial Materials [Member] | Cost of Sales [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 22,388,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 28,326,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Inventory Loss |  | 961,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 7,886,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Fixed Asset Write-offs and Other |  | 5,374,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 6,104,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2013 Rationalization Initiatives [Member] | Industrial Materials [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 89,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 59,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2013 Rationalization Initiatives [Member] | Industrial Materials [Member] | Employee Severance [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 433,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 17,072,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2013 Rationalization Initiatives [Member] | Industrial Materials [Member] | Special Termination Benefits [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 469,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 810,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2013 Rationalization Initiatives [Member] | Engineered Solutions [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 1,517,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 3,628,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
2013 Rationalization Initiatives [Member] | Engineered Solutions [Member] | Cost of Sales [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 827,000 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Inventory Loss |  | 485,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 896,000 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Fixed Asset Write-offs and Other |  | 233,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 2,274,000 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
2013 Rationalization Initiatives [Member] | Engineered Solutions [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
2013 Rationalization Initiatives [Member] | Engineered Solutions [Member] | Employee Severance [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | (28,000)us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 458,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
2013 Rationalization Initiatives [Member] | Engineered Solutions [Member] | Special Termination Benefits [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
2013 Rationalization Initiatives [Member] | Corporate and Other [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 1,816,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2013 Rationalization Initiatives [Member] | Corporate and Other [Member] | Cost of Sales [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Accelerated depreciation (recorded in Cost of sales) |  | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Inventory Loss |  | 0 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Fixed Asset Write-offs and Other |  | 0 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2013 Rationalization Initiatives [Member] | Corporate and Other [Member] | Selling, General and Administrative Expenses [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2013 Rationalization Initiatives [Member] | Corporate and Other [Member] | Employee Severance [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 1,816,000 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2013 Rationalization Initiatives [Member] | Corporate and Other [Member] | Special Termination Benefits [Member] | Rationalizations [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Incurred Cost |  | $ 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | $ 0 us-gaap_RestructuringAndRelatedCostIncurredCost / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |

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