v3.25.2
DEBT - Narrative (Details) - USD ($)
9 Months Ended
Jun. 27, 2025
Apr. 30, 2025
Sep. 30, 2024
May 26, 2021
Senior Secured Term Loan Facility due May 26, 2028 | Secured Debt        
Debt Instrument [Line Items]        
Debt instrument, basis spread on variable rate 2.00%      
Senior Secured Term Loan Facility due May 26, 2028 | Secured Debt | One-month interest period        
Debt Instrument [Line Items]        
Credit spread adjustment 0.11448%      
Senior Secured Term Loan Facility due May 26, 2028 | Secured Debt | Three-month interest period        
Debt Instrument [Line Items]        
Credit spread adjustment 0.26161%      
Senior Secured Term Loan Facility due May 26, 2028 | Secured Debt | Six-month interest period        
Debt Instrument [Line Items]        
Credit spread adjustment 0.42826%      
Senior Notes due June 2031 | Senior Notes        
Debt Instrument [Line Items]        
Debt face amount       $ 400,000,000
Debt instrument, interest rate, stated percentage       4.25%
Line of credit | ABL Credit Facility | Atkore International        
Debt Instrument [Line Items]        
Credit facility, aggregate commitments $ 325,000,000      
Credit facility available borrowing capacity $ 325,000,000   $ 325,000,000  
Line of credit | Amended ABL Credit Facility        
Debt Instrument [Line Items]        
Credit spread adjustment 0.10%      
Line of credit | Amended ABL Credit Facility | Minimum        
Debt Instrument [Line Items]        
Debt instrument, basis spread on variable rate 1.25%      
Line of credit | Amended ABL Credit Facility | Maximum        
Debt Instrument [Line Items]        
Debt instrument, basis spread on variable rate 1.75%      
Line of credit | Amended ABL Credit Facility | Secured Debt        
Debt Instrument [Line Items]        
Line of credit facility, term, outstanding obligations threshold amount   $ 100,000,000