Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Net sales and other operating revenues	$ 2,411	$ 2,871	$ 3,647
Cost of sales	1,833	2,286	2,926
Gross profit	578	585	721
Selling and administrative expenses	275	282	326
Research and technical expenses	53	58	60
Long-lived assets impairment charge (Note G)	23	210
Goodwill impairment charge (Note G)		352
Income (loss) from operations	250	(317)	335
Interest and dividend income	5	4	3
Interest expense	(54)	(53)	(55)
Other income (expense)	(7)	(11)	25
Income (loss) from continuing operations before income taxes and equity in earnings of affiliated companies	194	(377)	308
(Provision) benefit for income taxes	(34)	45	(92)
Equity in earnings of affiliated companies, net of tax	3	4
Income (loss) from continuing operations	163	(328)	216
Income (loss) from discontinued operations, net of tax of $1, $— and $2	1	2	2
Net income (loss)	164	(326)	218
Net income attributable to noncontrolling interests, net of tax of $4, $5 and $5	15	8	19
Net income (loss) attributable to Cabot Corporation	$ 149	$ (334)	$ 199
Weighted-average common shares outstanding, in millions:
Basic	62.4	63.4	64.4
Diluted	62.9	63.4	65.1
Basic:
Income (loss) from continuing operations attributable to Cabot Corporation	$ 2.36	$ (5.29)	$ 3.04
Income (loss) from discontinued operations	0.02	0.02	0.02
Net income (loss) attributable to Cabot Corporation	2.38	(5.27)	3.06
Diluted:
Income (loss) from continuing operations attributable to Cabot Corporation	2.34	(5.29)	3.01
Income (loss) from discontinued operations	0.02	0.02	0.02
Net income (loss) attributable to Cabot Corporation	2.36	(5.27)	3.03
Dividends per common share	$ 1.04	$ 0.88	$ 0.84
Purification Solutions [Member]
Long-lived assets impairment charge (Note G)		$ 210
Goodwill impairment charge (Note G)		$ 352