Goodwill and Other Intangibles - Summary of Goodwill by Reportable Segment (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Goodwill [Roll Forward]
Balance at beginning of period				$ 2,253
Impairment		$ (530)	$ 0	(530)	$ 0
Currency translation				0
Balance at end of period		1,723		1,723
Life Sciences [Member]
Goodwill [Roll Forward]
Balance at beginning of period				836
Impairment				0
Currency translation				(1)
Balance at end of period		835		835
Personal Care & Household [Member]
Goodwill [Roll Forward]
Balance at beginning of period				355
Impairment				(356)
Currency translation				1
Balance at end of period		0		0
Specialty Additives [Member]
Goodwill [Roll Forward]
Balance at beginning of period				609
Impairment				(174)
Currency translation				0
Balance at end of period		435		435
Performance Adhesives [Member]
Goodwill [Roll Forward]
Balance at beginning of period				453
Impairment				0
Currency translation				0
Balance at end of period		453		453
Intermediates and Solvents [Member]
Goodwill [Roll Forward]
Balance at beginning of period	[1]			0
Impairment	[1]			0
Currency translation	[1]			0
Balance at end of period	[1]	$ 0		$ 0

[1] As of March 31, 2020 and September 30, 2019, there was accumulated impairment of $90 million related to the Intermediates and Solvents reportable segment.