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Accounting Policies (Details Textual) | 12 Months Ended
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Dec. 31, 2012
Accounting policies (Textual) [Abstract] |
Maturity period of cash and cash equivalents | three months or less

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

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- Definition Maturity period of cash and cash equivalents. + References No definition available. + Details
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Namespace Prefix: | glt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration