Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues from external customers	$ 854	$ 705	$ 2,392	$ 1,994
Income (loss) from continuing operations before income taxes	95	68	16	221
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	822	679	2,308	1,913
Income (loss) from continuing operations before income taxes	127	99	367	301
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	32	26	84	81
Income (loss) from continuing operations before income taxes	(32)	(31)	(351)	(80)
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	466	367	1,307	1,014
Income (loss) from continuing operations before income taxes	74	51	215	145
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	274	229	771	662
Income (loss) from continuing operations before income taxes	56	46	160	146
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	70	71	206	207
Income (loss) from continuing operations before income taxes	(6)	(2)	(6)	4
Specialty Fluids [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	12	12	24	30
Income (loss) from continuing operations before income taxes	$ 3	$ 4	$ (2)	$ 6