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Significant Accounting Policies - Additional Information (Detail) - USD ($)
12 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2021
Significant Accounting Policies [Line Items]      
Equity affiliate investments $ 20,000,000 $ 20,000,000  
Capitalized interest 6,000,000 3,000,000 $ 1,000,000
Asset retirement obligation reserve 11,000,000 10,000,000  
Changes in allowance $ 0 0 0
Chance of utilizing the associated benefit for valuation allowances, maximum 50.00%    
Equity Method Investments [Member]      
Significant Accounting Policies [Line Items]      
Dividends declared $ 2,000,000 1,000,000 5,000,000
Minimum [Member]      
Significant Accounting Policies [Line Items]      
Payment terms 0 days    
Minimum [Member] | Buildings [Member]      
Significant Accounting Policies [Line Items]      
Useful life of property, plant and equipment 20 years    
Minimum [Member] | Machinery and Equipment [Member]      
Significant Accounting Policies [Line Items]      
Useful life of property, plant and equipment 10 years    
Minimum [Member] | Other Fixed Assets [Member]      
Significant Accounting Policies [Line Items]      
Useful life of property, plant and equipment 3 years    
Minimum [Member] | Cabot [Member] | Equity Affiliate Investments [Member]      
Significant Accounting Policies [Line Items]      
Equity method investment, ownership percentage 20.00%    
Maximum [Member]      
Significant Accounting Policies [Line Items]      
Payment terms 90 days    
Maximum [Member] | Buildings [Member]      
Significant Accounting Policies [Line Items]      
Useful life of property, plant and equipment 25 years    
Maximum [Member] | Machinery and Equipment [Member]      
Significant Accounting Policies [Line Items]      
Useful life of property, plant and equipment 25 years    
Maximum [Member] | Other Fixed Assets [Member]      
Significant Accounting Policies [Line Items]      
Useful life of property, plant and equipment 25 years    
Maximum [Member] | Cabot [Member] | Equity Affiliate Investments [Member]      
Significant Accounting Policies [Line Items]      
Equity method investment, ownership percentage 50.00%    
Other Nonoperating Income (Expense) [Member]      
Significant Accounting Policies [Line Items]      
Foreign currency transaction gain (loss) $ (35,000,000) $ (13,000,000) $ (6,000,000)