SEGMENT INFORMATION - Schedule of Net Sales From External Customers by Product Category (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Revenue from External Customer [Line Items]
Net sales	$ 2,850,378	$ 3,202,053	$ 3,518,761
Electrical
Revenue from External Customer [Line Items]
Net sales	1,998,209	2,354,958	2,675,050
Electrical | Operating Segments
Revenue from External Customer [Line Items]
Net sales	1,998,219	2,354,978	2,675,074
Electrical | Metal Electrical Conduit and Fittings
Revenue from External Customer [Line Items]
Net sales	455,678	551,753	529,083
Electrical | Plastic Pipe Conduit and Fittings
Revenue from External Customer [Line Items]
Net sales	673,622	921,587	1,252,422
Electrical | Electrical Cable and Flexible Conduit
Revenue from External Customer [Line Items]
Net sales	494,011	489,927	506,994
Electrical | Other Electrical products
Revenue from External Customer [Line Items]
Net sales	374,898	391,691	386,551
Safety & Infrastructure
Revenue from External Customer [Line Items]
Net sales	852,169	847,095	843,711
Safety & Infrastructure | Operating Segments
Revenue from External Customer [Line Items]
Net sales	853,369	849,077	844,158
Safety & Infrastructure | Mechanical Tube
Revenue from External Customer [Line Items]
Net sales	306,637	352,707	367,730
Safety & Infrastructure | Other Safety & Infrastructure products
Revenue from External Customer [Line Items]
Net sales	$ 545,532	$ 494,388	$ 475,982