Financial Information by Segment (Financial Information by Segment) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues from external customers	$ 820	[1]	$ 762	[1]
Income (loss) before taxes	41	[2]	55	[2]
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	475	[1]	489	[1]
Income (loss) before taxes	50	[2]	55	[2]
Performance Materials [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	196	[1]	205	[1]
Income (loss) before taxes	26	[2]	21	[2]
Advanced Technologies [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	38	[1]	39	[1]
Income (loss) before taxes	7	[2]	5	[2]
Purification Solutions [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	93	[1]
Income (loss) before taxes	7	[2]
Segment Total [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	802	[1]	733	[1]
Income (loss) before taxes	90	[2]	81	[2]
Unallocated And Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	18	[1],[2],[3]	29	[1],[2],[3]
Income (loss) before taxes	$ (49)	[2],[3]	$ (26)	[2],[3]

[1] Unallocated and other reflects royalties paid by equity affiliates, external shipping and handling fees, and the impact of the corporate adjustment for unearned revenue.

[2] Income (loss) from continuing operations before taxes that is categorized as Unallocated and Other includes:

[3] Unallocated and other includes certain items and eliminations necessary to reflect management's reporting of operating segment results. These items are reflective of the segment reporting presented to the Chief Operating Decision Maker.