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Divestitures - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from sale of business	$ 16		$ 16	$ 0
Income (loss) on acquisitions and divestitures	18	$ 0	(165)	$ (2)
Land and Building [Member] \| Composites Segment and the Intermediates and Solvents Marl Facility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from sale of business	11		11
Income (loss) on acquisitions and divestitures	11		11
Sale of properties with net book value	0		0
Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) on acquisitions and divestitures	8		8
Impairment charge	$ 0		183
Discontinued Operations, Held-for-sale [Member] \| Goodwill [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge			1
Discontinued Operations, Held-for-sale [Member] \| Other Intangible Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge			134
Discontinued Operations, Held-for-sale [Member] \| Property, Plant and Equipment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge			33
Discontinued Operations, Held-for-sale [Member] \| Operating Lease Assets Net [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge			14
Discontinued Operations, Held-for-sale [Member] \| Other Current Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge			$ 1