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v3.8.0.1

Segment and Geographic Information - Additional Information (Detail) - Customer | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Segment Reporting, Revenue Reconciling Item [Line Items] |  |  |
Number of customers accounting for percentage of net sales | 0 | 0 | 0
Customers accounted for certain percentage in net sales | 10.00% | 10.00% | 10.00%
Advanced Airlaid Materials [Member] |  |  |
Segment Reporting, Revenue Reconciling Item [Line Items] |  |  |
Number of customers accounting for percentage of net sales | 1 | 1 | 1

X
- Definition Entity wide revenue major customer threshold percentage. + References No definition available. + Details
Name: | glt_EntityWideRevenueMajorCustomerPercentageThreshold
Namespace Prefix: | glt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Number of customers accounting for percentage of net sales. + References No definition available. + Details
Name: | glt_NumberOfCustomersAccountingForPercentageOfNetSales
Namespace Prefix: | glt_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_SegmentReportingRevenueReconcilingItemLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=glt_AdvancedAirlaidMaterialsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |