REVENUE - TIMING OF REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Timing of Revenue Recognition [Roll Forward]
Customers' credit, beginning	$ 38,595	$ 44,910
Increase (decrease) for customers' credits	(15,746)	(20,032)
Customers' credit, end	22,849	24,878
Billed
Timing of Revenue Recognition [Roll Forward]
Billed, beginning	105,531	97,540
Increase (decrease) for customer accounts receivable	157,720	87,529
Billed, end	263,251	185,069
Unbilled
Timing of Revenue Recognition [Roll Forward]
Billed, beginning	20,094	19,100
Increase (decrease) for customer accounts receivable	53,531	55,356
Billed, end	$ 73,625	$ 74,456