Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 90	$ 106	$ 238	$ 140
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment, net of tax	(20)	(102)	117	(84)
Derivatives: net investment hedges
(Gains) losses reclassified to interest expense, net of tax	(1)	(1)	(4)	(4)
(Gains) losses excluded from effectiveness testing and amortized to interest expense, net of tax			1	1
Pension and other postretirement benefit liability adjustments, net of tax			(1)	2
Other comprehensive income (loss), net of tax of $-, $ -, $- and ($1)	(21)	(103)	113	(85)
Comprehensive income (loss)	69	3	351	55
Net income (loss) attributable to noncontrolling interests, net of tax	8	9	27	25
Foreign currency translation adjustment attributable to noncontrolling interests, net of tax	(6)	(9)	3	(6)
Comprehensive income (loss) attributable to noncontrolling interests	2		30	19
Comprehensive income (loss) attributable to Cabot Corporation	$ 67	$ 3	$ 321	$ 36