Pension And Other Post-Retirement Benefits (Schedule Of Components Of Net Periodic Benefit Cost For Pension And Other Post-Retirement Benefit Programs) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 144	$ 544
Interest cost	3,312	3,341
Expected return on plan assets	(4,407)	(4,558)
Amortization of prior service costs, gains or losses and net transition asset	4,024	2,814
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	0	81
Net periodic benefit cost	3,073	2,222
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	12	13
Interest cost	84	93
Amortization of prior service costs, gains or losses and net transition asset	(40)	(77)
Net periodic benefit cost	$ 56	$ 29

Pension And Other Post-Retirement Benefits (Schedule Of Components Of Net Periodic Benefit Cost For Pension And Other Post-Retirement Benefit Programs) (Details) (USD $)
In Thousands, unless otherwise specified

3 Months Ended

Mar. 31, 2015

Mar. 31, 2014

Pension Benefits

Defined Benefit Plan Disclosure [Line Items]

Service cost

$ 144us-gaap_DefinedBenefitPlanServiceCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

$ 544us-gaap_DefinedBenefitPlanServiceCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

Interest cost

3,312us-gaap_DefinedBenefitPlanInterestCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

3,341us-gaap_DefinedBenefitPlanInterestCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

Expected return on plan assets

(4,407)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

(4,558)us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

Amortization of prior service costs, gains or losses and net transition asset

4,024tg_AmortizationOfPriorServiceCostsAndNetGainsLoss
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

2,814tg_AmortizationOfPriorServiceCostsAndNetGainsLoss
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments

0us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

81us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

Net periodic benefit cost

3,073us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

2,222us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_PensionPlansDefinedBenefitMember

Other Post-Retirement Benefits

Defined Benefit Plan Disclosure [Line Items]

Service cost

12us-gaap_DefinedBenefitPlanServiceCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember

13us-gaap_DefinedBenefitPlanServiceCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember

Interest cost

84us-gaap_DefinedBenefitPlanInterestCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember

93us-gaap_DefinedBenefitPlanInterestCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember

Amortization of prior service costs, gains or losses and net transition asset

(40)tg_AmortizationOfPriorServiceCostsAndNetGainsLoss
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember

(77)tg_AmortizationOfPriorServiceCostsAndNetGainsLoss
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember

Net periodic benefit cost

$ 56us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember

$ 29us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember

- Definition

Amortization Of Prior Service Costs And Net Gains Loss

+ References

No definition available.

+ Details

Name:	tg_AmortizationOfPriorServiceCostsAndNetGainsLoss
Namespace Prefix:	tg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512136

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512171

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanInterestCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of net gain (loss) recognized in net periodic benefit cost due to settlements and curtailments. Curtailments result from an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services. Settlements result from an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include, but are not limited to, lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contracts to cover vested benefits.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Service Cost (Component of Net Periodic Pension Cost)

-URI http://asc.fasb.org/extlink&oid=6525008

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanServiceCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: