REVENUE - TIMING OF REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Timing of Revenue Recognition [Roll Forward]
Billed, beginning	$ 222,297
Customers' credit, beginning	33,246	$ 32,586
Increase (decrease) for customers' credits	(7,725)	(12,302)
Billed, end	194,453
Customers' credit, end	25,521	20,284
Billed
Timing of Revenue Recognition [Roll Forward]
Billed, beginning	222,297	212,838
Increase (decrease) for customer accounts receivable	(27,844)	60,475
Billed, end	194,453	273,313
Unbilled
Timing of Revenue Recognition [Roll Forward]
Billed, beginning	13,769	10,351
Increase (decrease) for customer accounts receivable	32,271	45,919
Billed, end	$ 46,040	$ 56,270