XML 65 R47.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 | Dec. 31, 2017
Income Tax Contingency [Line Items] |  |
Federal income tax rate | 21.00% | 35.00%
Increase in effective tax rate due to GILTI provisions | 10.00% |
Gross unrecognized tax benefits | $ 27.8 | $ 26.9
Unrecognized tax benefits that would impact effective tax rate | $ 17.6 |
Maximum [Member] |  |
Income Tax Contingency [Line Items] |  |
Percentage of deduction in GILTI Income | 50.00% |
Gross unrecognized tax benefits balance may decrease within the next twelve months | $ 4.9 |
Minimum [Member] |  |
Income Tax Contingency [Line Items] |  |
Gross unrecognized tax benefits balance may decrease within the next twelve months | 0.0 |
Internal Revenue Service [Member] |  |
Income Tax Contingency [Line Items] |  |
Additional income tax benefits | $ 0.2 |

X
- Definition Tax cuts and jobs act of 2017 additional income tax benefits. + References No definition available. + Details
Name: | glt_TaxCutsAndJobsActOf2017AdditionalIncomeTaxBenefits
Namespace Prefix: | glt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Tax cuts and jobs act of 2017 change in effective tax rate due to global intangible low-taxed income provisions. + References No definition available. + Details
Name: | glt_TaxCutsAndJobsActOf2017ChangeInEffectiveTaxRateDueToGlobalIntangibleLowTaxedIncomeProvisions
Namespace Prefix: | glt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tax cuts and jobs act of 2017, deduction in global intangible low taxed income, percentage. + References No definition available. + Details
Name: | glt_TaxCutsAndJobsActOf2017DeductionInGlobalIntangibleLowTaxedIncomePercentage
Namespace Prefix: | glt_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d)(3) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
Name: | us-gaap_DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
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_IncomeTaxContingencyLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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