Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Income Statement [Abstract]
Net sales and other operating revenues	$ 903	[1]	$ 846	[1]	$ 2,565	[1]	$ 2,452	[1]
Cost of sales	726		671		2,097		1,961
Gross profit	177		175		468		491
Selling and administrative expenses	73		68		223		199
Research and technical expenses	18		17		55		54
Income from operations	86		90		190		238
Interest and dividend income	2		1		4		3
Interest expense	(15)		(11)		(47)		(30)
Other (expense) income			(2)		3		(2)
Income from continuing operations before income taxes and equity in earnings of affiliated companies	73	[2]	78	[2]	150	[2]	209	[2]
Provision for income taxes	(16)		(16)		(51)		(55)
Equity in earnings of affiliated companies	3		4		9		8
Income from continuing operations	60		66		108		162
Income from discontinued operations, net of tax	2		4		1		204
Net income	62		70		109		366
Net income attributable to noncontrolling interests	3		4		3		14
Net income attributable to Cabot Corporation	$ 59		$ 66		$ 106		$ 352
Weighted-average common shares outstanding:
Basic	63.8		63.4		63.6		63.3
Diluted	64.5		64.3		64.3		64.2
Basic:
Income from continuing operations attributable to Cabot Corporation	$ 0.86		$ 0.97		$ 1.62		$ 2.32
Income from discontinued operations	$ 0.04		$ 0.07		$ 0.02		$ 3.18
Net income attributable to Cabot Corporation	$ 0.90		$ 1.04		$ 1.64		$ 5.50
Diluted:
Income from continuing operations attributable to Cabot Corporation	$ 0.86		$ 0.96		$ 1.61		$ 2.29
Income from discontinued operations	$ 0.04		$ 0.06		$ 0.02		$ 3.14
Net income attributable to Cabot Corporation	$ 0.90		$ 1.02		$ 1.63		$ 5.43
Dividends per common share	$ 0.20		$ 0.20		$ 0.60		$ 0.56

[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 are categorized as Unallocated and Other includes: