REVENUE - TIMING OF REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Timing of Revenue Recognition [Roll Forward]
Billed, beginning	$ 222,297
Customers' credit, beginning	33,246	$ 32,586
Increase (decrease) for customers' credits	(2,979)	(10,370)
Billed, end	110,463
Customers' credit, end	30,267	22,216
Billed
Timing of Revenue Recognition [Roll Forward]
Billed, beginning	222,297	212,838
Increase (decrease) for customer accounts receivable	(111,834)	55,205
Billed, end	110,463	268,043
Unbilled
Timing of Revenue Recognition [Roll Forward]
Billed, beginning	13,769	10,351
Increase (decrease) for customer accounts receivable	2,723	4,681
Billed, end	$ 16,492	$ 15,032