Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Net sales and other operating revenues	$ 958	$ 965
Cost of sales	740	784
Gross profit	218	181
Selling and administrative expenses	67	60
Research and technical expenses	15	13
Loss on sale of business		3
Income (loss) from operations	136	105
Interest and dividend income	9	6
Interest expense	(22)	(22)
Other income (expense)	(29)	(5)
Income (loss) from operations before income taxes and equity in earnings of affiliated companies	94	84
(Provision) benefit for income taxes	(34)	(20)
Equity in earnings of affiliated companies, net of tax	1	2
Net income (loss)	61	66
Net income (loss) attributable to noncontrolling interests, net of tax	11	12
Net income (loss) attributable to Cabot Corporation	$ 50	$ 54
Weighted-average common shares outstanding:
Basic	55.3	56.3
Diluted	55.8	56.7
Earnings (loss) per common share:
Basic	$ 0.88	$ 0.94
Diluted	$ 0.88	$ 0.93