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Investments (Narrative) (Details) (USD $)	12 Months Ended						0 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Apr. 02, 2007	Dec. 31, 2008
Investments, Other Investments [Line Items]
Gain (loss) on investment accounted for under the fair value method	$ 2,000,000us-gaap_UnrealizedGainLossOnInvestments		$ 3,400,000us-gaap_UnrealizedGainLossOnInvestments		$ 16,100,000us-gaap_UnrealizedGainLossOnInvestments
kaleo
Investments, Other Investments [Line Items]
Total cash invested in private company								7,500,000us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes / dei_LegalEntityAxis = tg_KaleoMember
Ownership interest percentage	20.00%us-gaap_VariableInterestEntityOwnershipPercentage / dei_LegalEntityAxis = tg_KaleoMember
Gain (loss) on investment accounted for under the fair value method	2,000,000us-gaap_UnrealizedGainLossOnInvestments / dei_LegalEntityAxis = tg_KaleoMember	[1]	3,400,000us-gaap_UnrealizedGainLossOnInvestments / dei_LegalEntityAxis = tg_KaleoMember	[1]	16,100,000us-gaap_UnrealizedGainLossOnInvestments / dei_LegalEntityAxis = tg_KaleoMember	[1]
Unrealized gain (loss) on investments, net of tax	1,000,000tg_UnrealizedGainLossOnInvestmentsNetOfTax / dei_LegalEntityAxis = tg_KaleoMember		2,200,000tg_UnrealizedGainLossOnInvestmentsNetOfTax / dei_LegalEntityAxis = tg_KaleoMember		10,200,000tg_UnrealizedGainLossOnInvestmentsNetOfTax / dei_LegalEntityAxis = tg_KaleoMember
Weighted average cost of capital	45.00%tg_FairValueInvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesWeightedAverageCostOfCapital / dei_LegalEntityAxis = tg_KaleoMember		55.00%tg_FairValueInvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesWeightedAverageCostOfCapital / dei_LegalEntityAxis = tg_KaleoMember		55.00%tg_FairValueInvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesWeightedAverageCostOfCapital / dei_LegalEntityAxis = tg_KaleoMember
Basis point decrease of weighted average cost of capital assumption	5.00%tg_PointDecreaseOfWeightedAverageCostOfCapitalAssumption / dei_LegalEntityAxis = tg_KaleoMember
Increase in fair value from five hundred point decrease in weighted average cost of capital assumption	6,000,000tg_IncreaseInFairValueFromFiveHundredPointDecreaseInWeightedAverageCostOfCapitalAssumption / dei_LegalEntityAxis = tg_KaleoMember
Basis point increase of weighted average cost of capital assumption	5.00%tg_PointIncreaseOfWeightedAverageCostOfCapitalAssumption / dei_LegalEntityAxis = tg_KaleoMember
Decrease in fair value from five hundred point increase in weighted average cost of capital assumption	6,000,000tg_DecreaseInFairValueFromFiveHundredPointIncreaseInWeightedAverageCostOfCapitalAssumption / dei_LegalEntityAxis = tg_KaleoMember
Harbinger
Investments, Other Investments [Line Items]
Total cash invested in private company							10,000,000us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember
Unrealized loss on investments under fair value method, other than temporary impairment	800,000us-gaap_CostmethodInvestmentsOtherThanTemporaryImpairment / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember		400,000us-gaap_CostmethodInvestmentsOtherThanTemporaryImpairment / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember		1,100,000us-gaap_CostmethodInvestmentsOtherThanTemporaryImpairment / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember
Unrealized loss on investments, net of tax	400,000tg_CostMethodInvestmentsOtherThanTemporaryImpairmentNetOfTax / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember		300,000tg_CostMethodInvestmentsOtherThanTemporaryImpairmentNetOfTax / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember		700,000tg_CostMethodInvestmentsOtherThanTemporaryImpairmentNetOfTax / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember
Withdrawal proceeds	200,000tg_TotalWithdrawalProceedsReceived / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember		400,000tg_TotalWithdrawalProceedsReceived / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember		500,000tg_TotalWithdrawalProceedsReceived / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember
Maximum | Harbinger
Investments, Other Investments [Line Items]
Percent ownership in investment (less than)							2.00%tg_PercentOwnershipInInvestment / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember / us-gaap_RangeAxis = us-gaap_MaximumMember
Other Assets and Deferred Charges [Member] | kaleo
Investments, Other Investments [Line Items]
Carrying value	39,100,000us-gaap_InvestmentOwnedAtFairValue / us-gaap_BalanceSheetLocationAxis = tg_OtherAssetsandDeferredChargesMember / dei_LegalEntityAxis = tg_KaleoMember		37,100,000us-gaap_InvestmentOwnedAtFairValue / us-gaap_BalanceSheetLocationAxis = tg_OtherAssetsandDeferredChargesMember / dei_LegalEntityAxis = tg_KaleoMember
Other Assets and Deferred Charges [Member] | Harbinger
Investments, Other Investments [Line Items]
Carrying value of investment	1,800,000us-gaap_CostMethodInvestments / us-gaap_BalanceSheetLocationAxis = tg_OtherAssetsandDeferredChargesMember / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember		2,800,000us-gaap_CostMethodInvestments / us-gaap_BalanceSheetLocationAxis = tg_OtherAssetsandDeferredChargesMember / dei_LegalEntityAxis = tg_HarbingerCapitalPartnersSpecialSituationsFundLPMember
Other Assets and Deferred Charges [Member] | Alleghany and Bath County, Virginia
Investments, Other Investments [Line Items]
Carrying value of investment	2,600,000us-gaap_CostMethodInvestments / us-gaap_BalanceSheetLocationAxis = tg_OtherAssetsandDeferredChargesMember / dei_LegalEntityAxis = tg_AlleghanyandBathCountyVirginiaMember		5,900,000us-gaap_CostMethodInvestments / us-gaap_BalanceSheetLocationAxis = tg_OtherAssetsandDeferredChargesMember / dei_LegalEntityAxis = tg_AlleghanyandBathCountyVirginiaMember
Alleghany and Bath County, Virginia
Investments, Other Investments [Line Items]
Gain (Loss) on Disposition of Assets	1,208,000us-gaap_GainLossOnDispositionOfAssets1 / dei_EntityByLocationAxis = tg_AlleghanyandBathCountyVirginiaMember		0us-gaap_GainLossOnDispositionOfAssets1 / dei_EntityByLocationAxis = tg_AlleghanyandBathCountyVirginiaMember		0us-gaap_GainLossOnDispositionOfAssets1 / dei_EntityByLocationAxis = tg_AlleghanyandBathCountyVirginiaMember
Unrealized Gain (Loss) on Investment Property	0tg_UnrealizedGainLossonInvestmentProperty / dei_EntityByLocationAxis = tg_AlleghanyandBathCountyVirginiaMember		1,018,000tg_UnrealizedGainLossonInvestmentProperty / dei_EntityByLocationAxis = tg_AlleghanyandBathCountyVirginiaMember		0tg_UnrealizedGainLossonInvestmentProperty / dei_EntityByLocationAxis = tg_AlleghanyandBathCountyVirginiaMember
Unrealized Gain Loss On Investment Property After Tax			(600,000)tg_UnrealizedGainLossOnInvestmentPropertyAfterTax / dei_EntityByLocationAxis = tg_AlleghanyandBathCountyVirginiaMember
Gain (Loss) on Sale of Investment Property, After Tax	$ (800,000)tg_GainLossonSaleofInvestmentPropertyAfterTax / dei_EntityByLocationAxis = tg_AlleghanyandBathCountyVirginiaMember
[1] See Notes 1, 3, 4 and 18 for more information on losses associated with plant shutdowns, asset impairments and restructurings, unusual items, gains or losses from sale of assets, gains or losses on an investment accounted for under the fair value method and other items.

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