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Long-Term Debt - Summary of Debts Borrowed by Subsidiary (Detail) - EUR (€) € in Thousands |  |  |  |  |  | 9 Months Ended |
--- | --- | --- | --- | --- | --- | --- | ---
May 04, 2016 | Apr. 26, 2016 | Oct. 10, 2015 | Sep. 04, 2014 | Apr. 11, 2013 | Sep. 30, 2020 | 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 |  |

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