XML 117 R91.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Retirement Plans and Other Post-Retirement Benefits - Schedule of Fair Value of Benefit Plan Assets (Detail) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | $ 673.1 | $ 610.7
Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 117.5 | 153.2
Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 555.6 | 457.5
Large Cap [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 214.9 | 201.9
Large Cap [Member] | Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 12.4 | 7.1
Large Cap [Member] | Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 202.5 | 194.8
Small and Mid Cap [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 46.2 | 50.9
Small and Mid Cap [Member] | Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 46.2 | 50.9
International Equity [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 81.4 | 79.5
International Equity [Member] | Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 7.2 | 38.8
International Equity [Member] | Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 74.2 | 40.7
Real Estate Investment Trusts (REIT) [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 27.6 | 27.9
Real Estate Investment Trusts (REIT) [Member] | Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 27.6 | 27.9
Fixed Income [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 290.9 | 237.7
Fixed Income [Member] | Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 24.0 | 28.5
Fixed Income [Member] | Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 266.9 | 209.2
Cash and Equivalents [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 12.1 | 12.8
Cash and Equivalents [Member] | Level 1 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | 0.1 |
Cash and Equivalents [Member] | Level 2 [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Fair value of plan assets | $ 12.0 | $ 12.8

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

X
- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=glt_LargeCapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=glt_SmallAndMidCapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=glt_InternationalEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=glt_RealEstateInvestmentTrustsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |