Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 82	$ 114	$ 148	$ 34
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment, net of tax	49	46	137	18
Derivatives: net investment hedges
(Gains) losses reclassified to interest expense, net of tax	(2)	(2)	(3)	(3)
(Gains) losses excluded from effectiveness testing and amortized to interest expense, net of tax	1	1	1	1
Pension and other postretirement benefit liability adjustments, net of tax	(1)	1	(1)	2
Other comprehensive income (loss), net of tax of $ - , $ - , $ - and $(1)	47	46	134	18
Comprehensive income (loss)	129	160	282	52
Net income (loss) attributable to noncontrolling interests, net of tax	7	7	19	16
Foreign currency translation adjustment attributable to noncontrolling interests, net of tax	3	1	9	3
Comprehensive income (loss) attributable to noncontrolling interests	10	8	28	19
Comprehensive income (loss) attributable to Cabot Corporation	$ 119	$ 152	$ 254	$ 33