REVENUE - TIMING OF REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Timing of Revenue Recognition [Roll Forward]
Billed, beginning balance	$ 222,297
Customers' credit, beginning balance	33,246	$ 32,586
Increase (decrease) for customers' credits	11,664	660
Billed, ending balance	97,540	222,297
Customers' credit, ending balance	44,910	33,246
Billed
Timing of Revenue Recognition [Roll Forward]
Billed, beginning balance	222,297	212,838
Increase (decrease) for customer accounts receivable	(124,757)	9,459
Billed, ending balance	97,540	222,297
Unbilled
Timing of Revenue Recognition [Roll Forward]
Billed, beginning balance	13,769	10,351
Increase (decrease) for customer accounts receivable	5,331	3,418
Billed, ending balance	$ 19,100	$ 13,769