XML 100 R84.htm IDEA: XBRL DOCUMENT
v3.21.2

Long-Term Debt - Summary of Debts Borrowed by Subsidiary (Detail) - EUR (€) € in Thousands |  |  |  |  |  | 6 Months Ended |
--- | --- | --- | --- | --- | --- | --- | ---
May 04, 2016 | Apr. 26, 2016 | Oct. 10, 2015 | Sep. 04, 2014 | Apr. 11, 2013 | Jun. 30, 2021 | Jul. 01, 2019
Debt Instrument [Line Items] |  |  |  |  |  |  |
Interest Rate |  |  |  |  |  |  | 1.25%
Maturity |  |  |  |  |  | Feb. 08, 2024 |
IKB Deutsche Industriebank AG Borrowing Agreements [Member] | Glatfelter Gernsbach GmbH [Member] | IKB Deutsche Industriebank AG Member |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Original Principal | € 7,195 | € 10,000 | € 2,608 | € 10,000 | € 42,700 |  |
Interest Rate | 1.55% | 1.30% | 1.55% | 2.40% | 2.05% |  |
Maturity | Sep. 30, 2025 | Jun. 30, 2023 | Sep. 30, 2025 | Jun. 30, 2022 | Mar. 31, 2023 |  |

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
Name: | us-gaap_DebtInstrumentMaturityDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DebtInstrumentAxis=glt_IKBDeutscheIndustriebankAGBorrowingAgreementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=glt_GlatfelterGernsbachGmbHMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LineOfCreditFacilityAxis=glt_IkbDeutscheIndustriebankAgMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |