XML 55 R39.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Income Taxes - Summary of Tax Years that Remain Subject to Examination by Major Jurisdiction (Detail) | 3 Months Ended
--- | ---
Mar. 31, 2017
United States - State [Member] | United States [Member] |
Income Tax Examination [Line Items] |
Examination in progress | 2014
Minimum [Member] | United States - Federal [Member] | United States [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2013
Minimum [Member] | United States - State [Member] | United States [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2012
Minimum [Member] | Foreign Tax Authority [Member] | Canada [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2010
Minimum [Member] | Foreign Tax Authority [Member] | Germany [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2012
Examination in progress | 2011
Minimum [Member] | Foreign Tax Authority [Member] | France [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2014
Examination in progress | 2011
Minimum [Member] | Foreign Tax Authority [Member] | United Kingdom [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2015
Minimum [Member] | Foreign Tax Authority [Member] | Philippines [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2015
Examination in progress | 2013
Maximum [Member] | United States - Federal [Member] | United States [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2016
Maximum [Member] | United States - State [Member] | United States [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2016
Maximum [Member] | Foreign Tax Authority [Member] | Canada [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2016
Maximum [Member] | Foreign Tax Authority [Member] | Germany [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2016
Examination in progress | 2013
Maximum [Member] | Foreign Tax Authority [Member] | France [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2016
Examination in progress | 2012
Maximum [Member] | Foreign Tax Authority [Member] | United Kingdom [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2016
Maximum [Member] | Foreign Tax Authority [Member] | Philippines [Member] |
Income Tax Examination [Line Items] |
Examinations not yet initiated | 2016
Examination in progress | 2014

X
- Definition Income tax examination in progress year. + References No definition available. + Details
Name: | glt_IncomeTaxExaminationInProgressYear
Namespace Prefix: | glt_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Income tax examination not yet initiated. + References No definition available. + Details
Name: | glt_IncomeTaxExaminationNotYetInitiated
Namespace Prefix: | glt_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- 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_IncomeTaxExaminationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalJurisdictionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_DomesticCountryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityAxis=us-gaap_ForeignCountryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_CA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_DE
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_FR
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_GB
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_PH
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |