v3.26.1
Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($)
 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Sep. 30, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair value, liabilities, Level 2 to Level 1 transfers, amount $ 0 $ 0  
Fair value, assets, Level 2 to Level 1 transfers, amount 0 0  
Fair value, liabilities, Level 1 to Level 2 transfers, amount 0 0  
Fair value, assets, Level 1 to Level 2 transfers, amount 0 0  
Fair value, assets, transfers into Level 3, amount 0 0  
Fair value, assets, transfers out of Level 3, amount 0 0  
Fair value, liabilities, transfers into Level 3, amount 0 0  
Fair value, liabilities, transfers out of Level 3, amount 0 $ 0  
Fixed Rate Debt [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Carrying value of long-term debt 1,060,000,000.00   $ 1,090,000,000.00
Fair value of long-term debt 1,040,000,000.00   1,090,000,000.00
Significant Observable Inputs (Level 2) [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other assets in the Consolidated Balance Sheets 9,000,000   9,000,000
Significant Observable Inputs (Level 2) [Member] | Net Investment Hedge [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other liabilities in the Consolidated Balance Sheets 3,000,000   12,000,000
Significant Observable Inputs (Level 2) [Member] | Forward Currency Contracts [Member] | Maximum [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other liabilities in the Consolidated Balance Sheets $ 1,000,000    
Other assets in the Consolidated Balance Sheets     $ 1,000,000