Financial Information by Segment & Geographic Area - Schedule of Performance Segment (Detail) - Performance Chemicals [Member] - Operating Segments [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Net sales	$ 933	$ 995	$ 1,028
Performance Additives [Member]
Segment Reporting Information [Line Items]
Net sales	645	694	707
Formulated Solutions [Member]
Segment Reporting Information [Line Items]
Net sales	$ 288	$ 301	$ 321