PROPERTY, PLANT AND EQUIPMENT - Summary of Property Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	$ 784,978	$ 763,542
Accumulated depreciation and amortization	(449,158)	(426,216)
Total	335,820	337,326
Land, building and building improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	156,393	133,036
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	577,573	580,698
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	$ 51,012	$ 49,808