Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Goodwill And Intangible Assets [Line Items]
Amortization expense estimated for year one	$ 6		$ 6
Amortization expense estimated for year two	6		6
Amortization expense estimated for year three	6		6
Amortization expense estimated for year four	6		6
Amortization expense estimated for year five	6		6
Cost of Sales, Selling and Administrative Expenses and Research and Technical Expenses [Member]
Goodwill And Intangible Assets [Line Items]
Amortization of intangible assets	$ 2	$ 1	$ 5	$ 4
Minimum [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets	10 years		10 years
Maximum [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets	25 years		25 years
Weighted Average [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets	16 years		16 years