Financial Information by Segment - Revenues From External Customers That are Categorized as Unallocated and Other Reflects Royalties, External Shipping and Handling Fees, The Impact of Unearned Revenue, Discounting Charges For Certain Notes Receivable, and Other By-product Revenue (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Revenues from external customers	$ 955	$ 958
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	33	32
Unallocated and Other [Member] | Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	28	30
Unallocated and Other [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	$ 5	$ 2