Financial Information By Segment (Schedule Of Performance Segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2012		Mar. 31, 2011
Segment Reporting Information [Line Items]
Net sales and other operating revenues	$ 844	[1]	$ 739	[1]	$ 1,606	[1]	$ 1,433	[1]
Performance Segment [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	235		222		440		412
Performance Segment [Member] | Performance Products Business [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	173		159		324		291
Performance Segment [Member] | Fumed Metal Oxides Business [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	$ 62		$ 63		$ 116		$ 121

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