PROPERTY, PLANT AND EQUIPMENT - Summary of property plant and equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 724,509	$ 696,667
Accumulated depreciation and amortization	(431,887)	(399,583)
Total	292,622	297,084
Land, building and building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	164,486	165,086
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	520,110	493,146
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 39,913	$ 38,435