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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, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting Information [Line Items]
Income (loss) on acquisitions and divestitures	$ 1	$ 0	$ 3	$ (165)
Goodwill impairment	0	706	0	706
Avoca [Member]
Segment Reporting Information [Line Items]
Income (loss) on acquisitions and divestitures	2		2	8
Impairment charge				183
Life Sciences [Member]
Segment Reporting Information [Line Items]
Goodwill impairment		375		375
Accelerated depreciation		8		21
Specialty Additives [Member]
Segment Reporting Information [Line Items]
Goodwill impairment		331		331
Accelerated depreciation		$ 19	3	$ 19
Personal Care [Member]
Segment Reporting Information [Line Items]
Accelerated depreciation			1
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Accelerated depreciation	$ 1		$ 1