XML 84 R68.htm IDEA: XBRL DOCUMENT
v3.20.2

Retirement Plans and Other Post-Retirement Benefits - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Jun. 30, 2020 | Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items] |  |  |
Employer contribution of employee’s eligible earnings, percentage |  |  | 10.00%
Pension settlement charge, net of post settlement adjustments | $ 389 |  | $ 6,792
Payment to third party related to qualified pension liabilities | $ 400 |  |
Pension Benefits [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension settlement charge, net of post settlement adjustments |  | $ 6,300 |
Reversion of excess pension plan assets |  | 55,500 |
Amount transferred to suspense account to fund future 401(k) contributions |  | 14,100 |
Accruing of excise taxes |  | 8,200 |
Available for general corporate purposes |  | $ 33,100 |

X
- Definition Defined benefit plan assets accruing of excise taxes. + References No definition available. + Details
Name: | glt_DefinedBenefitPlanAssetsAccruingOfExciseTaxes
Namespace Prefix: | glt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Defined benefit plan assets amount transferred to suspense account to fund future 401k contributions. + References No definition available. + Details
Name: | glt_DefinedBenefitPlanAssetsAmountTransferredToSuspenseAccountToFundFuture401KContributions
Namespace Prefix: | glt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Defined benefit plan assets available for general corporate purposes. + References No definition available. + Details
Name: | glt_DefinedBenefitPlanAssetsAvailableForGeneralCorporatePurposes
Namespace Prefix: | glt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Defined benefit plan reversion of excess pension plan assets. + References No definition available. + Details
Name: | glt_DefinedBenefitPlanReversionOfExcessPensionPlanAssets
Namespace Prefix: | glt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Defined benefit plan third party settlement. + References No definition available. + Details
Name: | glt_DefinedBenefitPlanThirdPartySettlement
Namespace Prefix: | glt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details
Name: | us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |