Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 66	$ (80)
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment, net of tax	88	(28)
Derivatives: net investment hedges
(Gains) losses reclassified to interest expense, net of tax	(1)	(1)
Pension and other postretirement benefit liability adjustments, net of tax		1
Other comprehensive income (loss), net of tax of ($1) and $ -	87	(28)
Comprehensive income (loss)	153	(108)
Net income (loss) attributable to noncontrolling interests, net of tax	12	9
Foreign currency translation adjustment attributable to noncontrolling interests, net of tax	6	2
Comprehensive income (loss) attributable to noncontrolling interests	18	11
Comprehensive income (loss) attributable to Cabot Corporation	$ 135	$ (119)