Financial Information by Segment - Revenues From External Customers That are Categorized as Unallocated and Other Reflect External Shipping and Handling Fees, The Impact of Unearned Revenue, Discounting Charges For Certain Notes Receivable (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting Information [Line Items]
Revenues from external customers	$ 923	$ 1,016	$ 2,814	$ 2,993
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	30	35	94	99
Unallocated and Other [Member] | Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	28	31	85	93
Unallocated and Other [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	$ 2	$ 4	$ 9	$ 6