Financial Information by Segment - Schedule of Performance 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]
Net sales	$ 678	$ 568	$ 1,289	$ 1,171
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	654	550	1,234	1,118
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	228	216	433	423
Performance Chemicals [Member] | Specialty Carbons and Formulations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	162	145	300	285
Performance Chemicals [Member] | Metal Oxides [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	$ 66	$ 71	$ 133	$ 138