Accumulated Other Comprehensive Income (Loss) ("AOCI") (Tables)

3 Months Ended

Dec. 31, 2024

Equity [Abstract]

Changes in Each Component of AOCI, Net of Tax

Changes in each component of AOCI, net of tax, were as follows:

	Currency Translation Adjustment			Pension and Other Post-retirement Benefit Liability Adjustments			Total
	(In millions)
Balance at September 30, 2024, attributable to Cabot Corporation	$	(342	)	$	(18	)	$	(360	)
Other comprehensive income (loss) before reclassifications		(104	)		—			(104	)
Amounts reclassified from AOCI		—			—			—
Less: Other comprehensive income (loss) attributable to    noncontrolling interests		(7	)		—			(7	)
Balance at December 31, 2024, attributable to Cabot Corporation	$	(439	)	$	(18	)	$	(457	)

	Currency Translation Adjustment			Pension and Other Post-retirement Benefit Liability Adjustments			Total
	(In millions)
Balance at September 30, 2023, attributable to Cabot Corporation	$	(353	)	$	(9	)	$	(362	)
Other comprehensive income (loss) before reclassifications		62			—			62
Amounts reclassified from AOCI		(1	)		—			(1	)
Less: Other comprehensive income (loss) attributable to    noncontrolling interests		4			—			4
Balance at December 31, 2023, attributable to Cabot Corporation	$	(296	)	$	(9	)	$	(305	)