Property, Plant and Equipment (Details) $ in Thousands	Sep. 30, 2023 USD ($) item	Sep. 30, 2022 USD ($) item
Property, plant and equipment
Gross amount	$ 395,729	$ 378,627
Less accumulated depreciation	(253,189)	(235,855)
Net amount	142,540	142,772
Finance lease assets	5,230	5,643
Shanghai
Property, plant and equipment
Finance lease assets	131	132
La Porte
Property, plant and equipment
Finance lease assets	$ 5,230	$ 5,643
Number of leased buildings | item	2	2
Land and Land Improvements [Member]
Property, plant and equipment
Gross amount	$ 10,418	$ 10,158
Building and Building Improvements [Member]
Property, plant and equipment
Gross amount	46,931	45,872
Machinery and Equipment [Member]
Property, plant and equipment
Gross amount	321,676	313,841
Construction in Progress [Member]
Property, plant and equipment
Gross amount	$ 16,704	$ 8,756