Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenues from external customers	$ 818	$ 678	$ 1,538	$ 1,289
Income (loss) from continuing operations before income taxes	(171)	78	(79)	153
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	794	654	1,486	1,234
Income (loss) from continuing operations before income taxes	127	107	240	202
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	24	24	52	55
Income (loss) from continuing operations before income taxes	(298)	(29)	(319)	(49)
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	454	352	841	647
Income (loss) from continuing operations before income taxes	79	54	141	94
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	268	228	497	433
Income (loss) from continuing operations before income taxes	57	51	104	100
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	66	67	136	136
Income (loss) from continuing operations before income taxes	(6)	2		6
Specialty Fluids [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	6	$ 7	12	18
Income (loss) from continuing operations before income taxes	$ (3)		$ (5)	$ 2