Financial Information by Segment - Schedule of Performance Segment (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Sales Information [Line Items]
Net sales	$ 694	$ 898	$ 1,506	$ 1,796
Operating Segments [Member]
Sales Information [Line Items]
Net sales	674	881	1,455	1,751
Performance Chemicals [Member] | Operating Segments [Member]
Sales Information [Line Items]
Net sales	237	264	466	501
Performance Chemicals [Member] | Specialty Carbons and Formulations [Member] | Operating Segments [Member]
Sales Information [Line Items]
Net sales	162	186	319	349
Performance Chemicals [Member] | Metal Oxides [Member] | Operating Segments [Member]
Sales Information [Line Items]
Net sales	$ 75	$ 78	$ 147	$ 152