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		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
Revenues from external customers	$ 1,019	$ 1,033	$ 1,977	$ 1,998
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	32	35	64	71
Unallocated and Other [Member] | Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	$ 32	36	62	69
Unallocated and Other [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		$ (1)	$ 2	$ 2