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Retirement Plans and Other Post-Retirement Benefits - Benefit Payments Expected under Non-Qualified Pension Plans and Other Benefit Plans (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2013
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Nonqualified Pension Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Benefit payments expected | $ 2,257
Other Benefit Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Benefit payments expected | $ 4,032

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- Definition Defined benefits plan expected benefit payments. + References No definition available. + Details
Name: | glt_DefinedBenefitsPlanExpectedBenefitPayments
Namespace Prefix: | glt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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