Long-Term Debt - Summary of Debts Borrowed by Subsidiary (Detail) - IKB Deutsche Industriebank AG Borrowing Agreements [Member] - Glatfelter Gernsbach GmbH and Co KG [Member] - IKB Deutsche Industriebank AG Member - EUR (€) € in Thousands	May 04, 2016	Apr. 26, 2016	Oct. 10, 2015	Sep. 04, 2014	Apr. 11, 2013
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