Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Revenues from external customers	$ 678	$ 568	$ 1,289	$ 1,171
Income (loss) from continuing operations before income taxes	78	62	151	54
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	654	550	1,234	1,118
Income (loss) from continuing operations before income taxes	107	88	202	159
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	24	18	55	53
Income (loss) from continuing operations before income taxes	(29)	(26)	(51)	(105)
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	352	261	647	549
Income (loss) from continuing operations before income taxes	54	34	94	60
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	228	216	433	423
Income (loss) from continuing operations before income taxes	51	58	100	108
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	67	67	136	133
Income (loss) from continuing operations before income taxes	2	(2)	6	(7)
Specialty Fluids [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	$ 7	6	18	13
Income (loss) from continuing operations before income taxes		$ (2)	$ 2	$ (2)