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Rationalizations and Impairments (Rationalization Costs Incurred) (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended
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Mar. 31, 2015 | Mar. 31, 2014
Rationalization Plan |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | $ 6,503 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | $ 17,855 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember
Rationalization Plan | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 433 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 17,433 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember
Inventory loss | 742 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 805 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember
Fixed asset write-offs and other | 1,144 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | (494)gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember
Rationalization Plan | Research and Development |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 621 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Rationalization Plan | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other | 1,069 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 25 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember
Rationalization Plan | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Contract terminations | 75 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember |
Rationalization Plan | Industrial Materials |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 1,693 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 17,480 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
Rationalization Plan | Industrial Materials | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 433 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 17,020 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
Inventory loss | (61)gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 815 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
Fixed asset write-offs and other | 1,243 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | (494)gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
Rationalization Plan | Industrial Materials | Research and Development |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Rationalization Plan | Industrial Materials | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other | 0 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 25 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
Rationalization Plan | Industrial Materials | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Contract terminations | 25 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
Rationalization Plan | Engineered Solutions |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 3,123 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 375 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
Rationalization Plan | Engineered Solutions | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 413 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
Inventory loss | 803 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | (10)gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
Fixed asset write-offs and other | (99)gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Rationalization Plan | Engineered Solutions | Research and Development |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Rationalization Plan | Engineered Solutions | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other | 3 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 0 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
Rationalization Plan | Engineered Solutions | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Contract terminations | 50 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
Rationalization Plan | Corporate, R&D and Other |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 1,687 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember
Rationalization Plan | Corporate, R&D and Other | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 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 | Corporate, R&D and Other | Research and Development |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 621 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Rationalization Plan | Corporate, R&D and Other | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other | 1,066 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember
Rationalization Plan | Corporate, R&D and Other | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Contract terminations | 0 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
Rationalization Plan | Employee Severance | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 2,419 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember | 86 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember
Rationalization Plan | Employee Severance | Industrial Materials | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 53 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 114 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
Rationalization Plan | Employee Severance | Engineered Solutions | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 2,366 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | (28)us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
Rationalization Plan | Employee Severance | Corporate, R&D and Other | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 0 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_RationalizationPlanMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_SeveranceCosts1 / 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 |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 1,736 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 17,855 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember
2013 Rationalization Initiatives | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 433 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 17,433 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember
Inventory loss | (61)gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 805 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember
Fixed asset write-offs and other | 1,252 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | (494)gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember
2013 Rationalization Initiatives | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other |  | 25 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember
2013 Rationalization Initiatives | Industrial Materials |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 1,727 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 17,480 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
2013 Rationalization Initiatives | Industrial Materials | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 433 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 17,020 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
Inventory loss | (61)gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 815 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
Fixed asset write-offs and other | 1,243 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | (494)gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
2013 Rationalization Initiatives | Industrial Materials | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other |  | 25 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
2013 Rationalization Initiatives | Engineered Solutions |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 9 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 375 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
2013 Rationalization Initiatives | Engineered Solutions | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 413 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
Inventory loss | 0 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | (10)gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
Fixed asset write-offs and other | 9 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | 0 gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
2013 Rationalization Initiatives | Engineered Solutions | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other |  | 0 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
2013 Rationalization Initiatives | Corporate, R&D and Other |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 0 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember
2013 Rationalization Initiatives | Corporate, R&D and Other | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 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 | Corporate, R&D and Other | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other |  | 0 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember
2013 Rationalization Initiatives | Employee Severance | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 87 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember | 86 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember
2013 Rationalization Initiatives | Employee Severance | Industrial Materials | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 87 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember | 114 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember
2013 Rationalization Initiatives | Employee Severance | Engineered Solutions | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 0 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember | (28)us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember
2013 Rationalization Initiatives | Employee Severance | Corporate, R&D and Other | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 0 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember | 0 us-gaap_SeveranceCosts1 / 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 | Contract Terminations | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Contract terminations | 25 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember |
2013 Rationalization Initiatives | Contract Terminations | Industrial Materials | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Contract terminations | 25 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2013 Rationalization Initiatives | Contract Terminations | Engineered Solutions | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Contract terminations | 0 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = gti_EngineeredSolutionsMember |
2013 Rationalization Initiatives | Contract Terminations | Corporate, R&D and Other | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Contract terminations | 0 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_SpecialTerminationBenefitsMember / us-gaap_RestructuringPlanAxis = gti_A2013RationalizationInitiativesMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2014 Engineered Solutions Rationalization |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 465 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2014EngineeredSolutionsRationalizationMember |
2014 Engineered Solutions Rationalization | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Inventory loss | 434 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2014EngineeredSolutionsRationalizationMember |
Fixed asset write-offs and other | (3)gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2014EngineeredSolutionsRationalizationMember |
2014 Engineered Solutions Rationalization | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | (16)us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_A2014EngineeredSolutionsRationalizationMember |
Contract terminations | 50 gti_RestructuringandRelatedCostContractTermination / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringPlanAxis = gti_A2014EngineeredSolutionsRationalizationMember |
2014 Corporate and Research & Development Rationalization | Industrial Materials |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | (34)us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2014CorporateandResearchDevelopmentRationalizationMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2014 Corporate and Research & Development Rationalization | Industrial Materials | Research and Development |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 0 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_A2014CorporateandResearchDevelopmentRationalizationMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2014 Corporate and Research & Development Rationalization | Industrial Materials | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other | 0 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2014CorporateandResearchDevelopmentRationalizationMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2014 Corporate and Research & Development Rationalization | Corporate, R&D and Other |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 1,687 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2014CorporateandResearchDevelopmentRationalizationMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2014 Corporate and Research & Development Rationalization | Corporate, R&D and Other | Research and Development |  |
Restructuring Cost and Reserve [Line Items] |  |
Accelerated depreciation | 621 us-gaap_RestructuringReserveAcceleratedDepreciation / us-gaap_IncomeStatementLocationAxis = us-gaap_ResearchAndDevelopmentExpenseMember / us-gaap_RestructuringPlanAxis = gti_A2014CorporateandResearchDevelopmentRationalizationMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2014 Corporate and Research & Development Rationalization | Corporate, R&D and Other | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other | 1,066 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2014CorporateandResearchDevelopmentRationalizationMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2014 Corporate and Research & Development Rationalization | Employee Severance | Industrial Materials | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | (34)us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2014CorporateandResearchDevelopmentRationalizationMember / us-gaap_StatementBusinessSegmentsAxis = gti_IndustrialMaterialsMember |
2014 Corporate and Research & Development Rationalization | Employee Severance | Corporate, R&D and Other | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | 0 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2014CorporateandResearchDevelopmentRationalizationMember / us-gaap_StatementBusinessSegmentsAxis = us-gaap_CorporateAndOtherMember |
2015 Advanced Graphite Materials Rationalization |  |
Restructuring Cost and Reserve [Line Items] |  |
Total rationalization plan and related charges | 2,649 us-gaap_RestructuringCosts / us-gaap_RestructuringPlanAxis = gti_A2015AdvancedGraphiteMaterialsRationalizationMember |
2015 Advanced Graphite Materials Rationalization | Cost of Sales |  |
Restructuring Cost and Reserve [Line Items] |  |
Inventory loss | 369 gti_RestructuringandRelatedCostInventoryLoss / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2015AdvancedGraphiteMaterialsRationalizationMember |
Fixed asset write-offs and other | (105)gti_RestructuringandRelatedCostFixedAssetWriteoffsandOther / us-gaap_IncomeStatementLocationAxis = us-gaap_CostOfSalesMember / us-gaap_RestructuringPlanAxis = gti_A2015AdvancedGraphiteMaterialsRationalizationMember |
2015 Advanced Graphite Materials Rationalization | Selling and Administrative |  |
Restructuring Cost and Reserve [Line Items] |  |
Other | 3 us-gaap_OtherRestructuringCosts / us-gaap_IncomeStatementLocationAxis = us-gaap_SellingGeneralAndAdministrativeExpensesMember / us-gaap_RestructuringPlanAxis = gti_A2015AdvancedGraphiteMaterialsRationalizationMember |
2015 Advanced Graphite Materials Rationalization | Employee Severance | Rationalizations |  |
Restructuring Cost and Reserve [Line Items] |  |
Severance and related costs | $ 2,382 us-gaap_SeveranceCosts1 / us-gaap_IncomeStatementLocationAxis = gti_RationalizationsMember / us-gaap_RestructuringCostAndReserveAxis = us-gaap_EmployeeSeveranceMember / us-gaap_RestructuringPlanAxis = gti_A2015AdvancedGraphiteMaterialsRationalizationMember |

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