Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Net sales and other operating revenues	$ 1,149	$ 917	$ 3,209	$ 2,505
Cost of sales	914	703	2,544	1,884
Gross profit	235	214	665	621
Selling and administrative expenses	51	68	196	200
Research and technical expenses	14	12	41	41
Loss on sale of business and asset impairment charge (Note D)	2		206
Gain on bargain purchase of a business (Note C)			(24)
Income (loss) from operations	168	134	246	380
Interest and dividend income		2	7	6
Interest expense	(15)	(12)	(38)	(37)
Other income (expense)	(1)	(1)	(9)	(9)
Income (loss) before income taxes and equity in earnings of affiliated companies	152	123	206	340
(Provision) benefit for income taxes	(49)	(30)	(73)	(93)
Equity in earnings of affiliated companies, net of tax	3	2	7	3
Net income (loss)	106	95	140	250
Net income (loss) attributable to noncontrolling interests, net of tax	9	9	25	29
Net income (loss) attributable to Cabot Corporation	$ 97	$ 86	$ 115	$ 221
Weighted-average common shares outstanding:
Basic	56.3	56.7	56.5	56.7
Diluted	56.8	57.0	56.9	56.8
Earnings (loss) per common share:
Basic	$ 1.70	$ 1.48	$ 2.00	$ 3.85
Diluted	$ 1.69	$ 1.48	$ 1.99	$ 3.84