Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Revenues from external customers	$ 968	$ 1,149	$ 2,966	$ 3,209
Income (loss) before income taxes	130	152	324	206
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	931	1,106	2,858	3,089
Income (loss) before income taxes	164	176	437	484
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	37	43	108	120
Income (loss) before income taxes	(34)	(24)	(113)	(278)
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		23	72
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	624	730	1,939	1,947
Income (loss) before income taxes	132	113	348	299
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		4	11
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	307	376	919	1,045
Income (loss) before income taxes	$ 32	$ 63	$ 89	185
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers				$ 97