Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Revenues from external customers	$ 1,149	$ 917	$ 3,209	$ 2,505
Income (loss) before income taxes	152	123	206	340
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	1,079	851	3,006	2,343
Income (loss) before income taxes	176	145	484	434
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	70	66	203	162
Income (loss) before income taxes	(24)	(22)	(278)	(94)
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	707	479	1,875	1,288
Income (loss) before income taxes	113	85	299	262
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	372	303	1,034	864
Income (loss) before income taxes	$ 63	54	185	166
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		69	$ 97	191
Income (loss) before income taxes		$ 6		$ 6