RESTRUCTURING CHARGES - Summary of accrued liability for the restructuring and related charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	$ 19,658	$ 650	$ 682
Charges	41,309	92,468	16,782
Payments	(24,206)	(14,528)	(11,983)
Non-cash charges	(23,763)	(58,932)	(4,831)
Restructuring reserve, ending balance	12,998	19,658	650
Personnel related costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	14,107	386	418
Charges	5,856	16,772	4,124
Payments	(11,781)	(3,051)	(4,156)
Non-cash charges	0	0	0
Restructuring reserve, ending balance	8,182	14,107	386
Facilities & Exit Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	5,551	264	264
Charges	11,690	16,764	7,827
Payments	(12,425)	(11,477)	(7,827)
Non-cash charges	0	0	0
Restructuring reserve, ending balance	4,816	5,551	264
Facility and Other Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	0	0	0
Charges	23,763	58,932	4,831
Payments	0	0	0
Non-cash charges	(23,763)	(58,932)	(4,831)
Restructuring reserve, ending balance	$ 0	$ 0	$ 0