Financial Information by Segment - Financial Information by Reportable Segment (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
Income (loss) before income taxes	110	147	194	54
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	998	1,053	1,927	1,983
Income (loss) before income taxes	150	171	273	308
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	35	39	71	77
Income (loss) before income taxes	(40)	(24)	(79)	(254)
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		49	27
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	672	654	1,315	1,217
Income (loss) before income taxes	122	101	216	186
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		7	3
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	326	363	612	669
Income (loss) before income taxes	$ 28	70	$ 57	122
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		$ 36		$ 97