RESTRUCTURING CHARGES - Summary of accrued liability for the restructuring and related charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	$ 682	$ 845	$ 0
Charges	16,782	21,418	13,669
Payments	(11,983)	(14,926)	(8,132)
Non-cash charges	(4,831)	(6,655)	(4,692)
Restructuring reserve, ending balance	650	682	845
Personnel Related Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	418	581	0
Charges	4,124	3,190	5,620
Payments	(4,156)	(3,353)	(5,039)
Non-cash charges	0	0	0
Restructuring reserve, ending balance	386	418	581
Facilities & Exit Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	264	264	0
Charges	7,827	11,573	3,357
Payments	(7,827)	(11,573)	(3,093)
Non-cash charges			0
Restructuring reserve, ending balance	264	264	264
Non Cash Facility and Other Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	0	0	0
Charges	4,831	6,655	4,692
Payments	0	0	0
Non-cash charges	(4,831)	(6,655)	(4,692)
Restructuring reserve, ending balance	$ 0	$ 0	$ 0