Financial Information by Segment - Sales of Equity Method Affiliate and Discounting Charges for Certain Notes Receivable, by-product Revenue and Indirect Tax Settlement Credits (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Revenues from external customers	$ 1,149	$ 917	$ 3,209	$ 2,505
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	70	66	203	162
Unallocated and Other [Member] | Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	44	41	124	112
Unallocated and Other [Member] | By-product Sales [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	28	19	89	54
Unallocated and Other [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	$ (2)	$ 6	$ (10)	$ (4)