v3.23.1
Financial Instruments and Risk Management - Narrative (Details)
3 Months Ended 6 Months Ended 12 Months Ended
Mar. 31, 2023
USD ($)
derivative_instrument
Contract
Mar. 31, 2022
USD ($)
Mar. 31, 2023
USD ($)
derivative_instrument
Contract
Mar. 31, 2022
USD ($)
Sep. 30, 2021
USD ($)
Sep. 30, 2022
USD ($)
Jan. 22, 2021
USD ($)
Dec. 22, 2020
USD ($)
Derivative [Line Items]                
Unrecognized pre-tax loss     $ 68,500,000   $ (86,400,000)      
Portion or pre-tax gain included in AOCI expected to be included in earnings $ (700,000)   (700,000)          
Interest Rate Contracts                
Derivative [Line Items]                
Notional value $ 550,000,000.0   $ 550,000,000.0       $ 700,000,000.0 $ 550,000,000.0
Notional value decrease each year             $ 100,000,000.0  
Interest Rate Contracts | LIBOR                
Derivative [Line Items]                
Fixed interest rate 0.95%   0.95%         0.95%
Line of Credit | Senior Secured Term Loan B Facility, net of discount, due 2022                
Derivative [Line Items]                
Face amount of debt $ 1,051,000,000   $ 1,051,000,000          
Estimate of Fair Value                
Derivative [Line Items]                
Fair market value of fixed rate long-term debt 2,091,300,000   2,091,300,000     $ 1,795,700,000    
Reported Value Measurement                
Derivative [Line Items]                
Fair market value of fixed rate long-term debt 2,379,500,000   2,379,500,000     2,337,100,000    
Designated as Hedging Instrument | Cash Flow Hedging                
Derivative [Line Items]                
Derivatives - Foreign Currency contracts 64,300,000   64,300,000     96,600,000    
Designated as Hedging Instrument | Cash Flow Hedging | Zinc contracts                
Derivative [Line Items]                
Derivatives - Foreign Currency contracts $ (3,500,000)   $ (3,500,000)     (6,100,000)    
Derivative, Number of Open Contracts | Contract 16   16          
Notional value $ 44,000,000   $ 44,000,000          
Designated as Hedging Instrument | Cash Flow Hedging | Foreign currency contracts                
Derivative [Line Items]                
Derivatives - Foreign Currency contracts (700,000)   (700,000)     16,300,000    
Notional value $ 177,000,000   $ 177,000,000          
Number of open contracts | derivative_instrument 68   68          
Not Designated as Hedging Instrument | Foreign currency contracts                
Derivative [Line Items]                
Derivatives - Foreign Currency contracts $ (200,000)   $ (200,000)     $ (600,000)    
Gain (Loss) Recognized in Income 100,000 $ 1,500,000 600,000 $ 3,400,000        
Not Designated as Hedging Instrument | Foreign currency contracts                
Derivative [Line Items]                
Notional value $ 118,000,000   $ 118,000,000          
Number of open contracts | derivative_instrument 8   8