Financial Information by Segment - Financial Information by Reportable Segment (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Revenues from external customers	$ 1,033	$ 1,092	$ 1,998	$ 2,060
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		49	27
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		$ 7	$ 3