Financial Information by Segment & Geographic Area - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues from external customers	$ 3,409	$ 2,614	$ 3,337
Depreciation and amortization	160	158	148
Equity in earnings of affiliated companies	3	3	1
Income (loss) from continuing operations before income taxes	406	(33)	255
Assets	3,306	2,781	3,004
Total expenditures for additions to long-lived assets	198	169	247
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	3,186	2,442	3,144
Depreciation and amortization	159	156	147
Equity in earnings of affiliated companies	4	4	3
Income (loss) from continuing operations before income taxes	550	283	444
Assets	3,029	2,518	2,637
Total expenditures for additions to long-lived assets	193	166	242
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	223	172	193
Depreciation and amortization	1	2	1
Equity in earnings of affiliated companies	(1)	(1)	(2)
Income (loss) from continuing operations before income taxes	(144)	(316)	(189)
Assets	277	263	367
Total expenditures for additions to long-lived assets	5	3	5
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	1,781	1,256	1,815
Depreciation and amortization	70	68	69
Equity in earnings of affiliated companies			(1)
Income (loss) from continuing operations before income taxes	329	162	266
Assets	1,421	1,077	1,177
Total expenditures for additions to long-lived assets	104	66	82
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	1,148	933	995
Depreciation and amortization	73	64	51
Equity in earnings of affiliated companies	2	1	1
Income (loss) from continuing operations before income taxes	211	118	152
Assets	1,325	1,145	1,024
Total expenditures for additions to long-lived assets	80	92	148
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	257	253	278
Depreciation and amortization	16	24	26
Equity in earnings of affiliated companies	2	3	3
Income (loss) from continuing operations before income taxes	10	3	2
Assets	283	296	436
Total expenditures for additions to long-lived assets	$ 9	$ 8	11
Specialty Fluids [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers			56
Depreciation and amortization			1
Income (loss) from continuing operations before income taxes			24
Total expenditures for additions to long-lived assets			$ 1