INTANGIBLE ASSETS - Summary of intangible assets - Useful life (Details)	12 Months Ended
	Sep. 30, 2021
Internally developed software
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life (in years)	5 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life (in years)	10 years
Intellectual property | Minimum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life (in years)	5 years
Intellectual property | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life (in years)	15 years