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Reportable Segment Information - Summary of Financial Information for Each Reportable Segment (Parenthetical) (Details) - 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]
Income (loss) on acquisitions and divestitures	$ (0)	$ (99)	$ (165)	$ (100)
Goodwill impairment - Note G	706	0	706	0
Avoca [Member]
Segment Reporting Information [Line Items]
Income (loss) on acquisitions and divestitures			8
Impairment charge			183
Nutraceuticals [Member]
Segment Reporting Information [Line Items]
Impairment charge		99		99
Life Sciences [Member]
Segment Reporting Information [Line Items]
Goodwill impairment - Note G	375		375
Accelerated depreciation	8		21
Specialty Additives [Member]
Segment Reporting Information [Line Items]
Goodwill impairment - Note G	331		331
Accelerated depreciation	$ 19	7	$ 19	55
Personal Care [Member]
Segment Reporting Information [Line Items]
Accelerated depreciation		$ 1		$ 1