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