SEGMENT INFORMATION - Reconciliation of Operating Segment Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Unallocated expenses	$ (53,309)	$ (46,610)	$ (65,956)
Depreciation and amortization	(124,533)	(121,018)	(115,524)
Interest expense, net	(33,269)	(35,584)	(35,232)
Loss on extinguishment of debt	(795)	0	0
Asset impairment charges	(214,386)	0	0
Stock-based compensation	(23,561)	(20,300)	(21,101)
Transaction costs	(291)	(140)	(968)
Gain on purchase of business	(6,243)	0	0
Loss on assets held for sale	(257)	(733)	(7,477)
Other	(1,649)	(6,701)	(11,535)
(Loss) Income before income taxes	(18,590)	587,237	850,290
Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	439,703	818,323	1,108,083
Operating Segments | Electrical
Segment Reporting Information [Line Items]
Adjusted EBITDA	330,512	728,341	1,004,853
Operating Segments | Safety & Infrastructure
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 109,191	$ 89,982	$ 103,231