Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 106	$ 95	$ 140	$ 250
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment, net of tax	(102)	71	(84)	89
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		2	2	6
Other comprehensive income (loss), net of tax of $ —, $1, ($1), and ($2)	(103)	72	(85)	92
Comprehensive income (loss)	3	167	55	342
Net income (loss) attributable to noncontrolling interests, net of tax	9	9	25	29
Foreign currency translation adjustment attributable to noncontrolling interests, net of tax	(9)	3	(6)	8
Comprehensive income (loss) attributable to noncontrolling interests		12	19	37
Comprehensive income (loss) attributable to Cabot Corporation	$ 3	$ 155	$ 36	$ 305