Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Net sales and other operating revenues	$ 968	$ 1,149	$ 2,966	$ 3,209
Cost of sales	745	914	2,352	2,544
Gross profit	223	235	614	665
Selling and administrative expenses	58	51	184	196
Research and technical expenses	15	14	43	41
Loss on sale of business and asset impairment charge (Note D)		2	3	206
Gain on bargain purchase of a business (Note C)				(24)
Income (loss) from operations	150	168	384	246
Interest and dividend income	7		22	7
Interest expense	(24)	(15)	(69)	(38)
Other income (expense)	(3)	(1)	(13)	(9)
Income (loss) before income taxes and equity in earnings of affiliated companies	130	152	324	206
(Provision) benefit for income taxes	(41)	(49)	(90)	(73)
Equity in earnings of affiliated companies, net of tax	1	3	4	7
Net income (loss)	90	106	238	140
Net income (loss) attributable to noncontrolling interests, net of tax	8	9	27	25
Net income (loss) attributable to Cabot Corporation	$ 82	$ 97	$ 211	$ 115
Weighted-average common shares outstanding:
Basic	56.1	56.3	56.2	56.5
Diluted	56.5	56.8	56.7	56.9
Earnings (loss) per common share:
Basic	$ 1.44	$ 1.70	$ 3.68	$ 2.00
Diluted	$ 1.43	$ 1.69	$ 3.65	$ 1.99