Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Income Statement [Abstract]
Net sales and other operating revenues	$ 1,033	$ 1,092	$ 1,998	$ 2,060
Cost of sales	823	860	1,607	1,630
Gross profit	210	232	391	430
Selling and administrative expenses	66	74	126	145
Research and technical expenses	15	14	28	27
Loss on sale of business and asset impairment charge (Note D)		7	3	204
Gain on bargain purchase of a business (Note C)		(24)		(24)
Income (loss) from operations	129	161	234	78
Interest and dividend income	9	4	15	7
Interest expense	(23)	(11)	(45)	(23)
Other income (expense)	(5)	(7)	(10)	(8)
Income (loss) before income taxes and equity in earnings of affiliated companies	110	147	194	54
(Provision) benefit for income taxes	(29)	(36)	(49)	(24)
Equity in earnings of affiliated companies, net of tax	1	3	3	4
Net income (loss)	82	114	148	34
Net income (loss) attributable to noncontrolling interests, net of tax	7	7	19	16
Net income (loss) attributable to Cabot Corporation	$ 75	$ 107	$ 129	$ 18
Weighted-average common shares outstanding:
Basic	56.3	56.6	56.3	56.5
Diluted	56.8	57.1	56.7	56.9
Earnings (loss) per common share:
Basic	$ 1.31	$ 1.86	$ 2.24	$ 0.30
Diluted	$ 1.29	$ 1.84	$ 2.23	$ 0.30