Divestitures - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Aug. 30, 2019	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Stranded divestitures costs		$ 0	$ 12	$ 0	$ 23
Composites Segment and the Intermediates and Solvents Facility [Member] | INEOS Enterprises [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from sale of business	$ 1,015
Transition service fee income recognized		$ 3		$ 6