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Plant, Equipment and Timberlands - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | Dec. 31, 2013 | Dec. 31, 2012
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Property Plant And Equipment Useful Life And Values [Abstract] |  |
Accrued capital expenditures | $ 11.9 | $ 21.7

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- Definition Accrued Capital Expenditures + References No definition available. + Details
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Namespace Prefix: | glt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
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Namespace Prefix: | glt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration