Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues from external customers	$ 821	$ 720
Income (loss) from continuing operations before income taxes	70	92
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	772	692
Income (loss) from continuing operations before income taxes	105	113
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	49	28
Income (loss) from continuing operations before income taxes	(35)	(21)
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	457	387
Income (loss) from continuing operations before income taxes	62	62
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	231	229
Income (loss) from continuing operations before income taxes	36	47
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	65	70
Income (loss) from continuing operations before income taxes	(3)	6
Specialty Fluids [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	19	6
Income (loss) from continuing operations before income taxes	$ 10	$ (2)