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

3 Months Ended

Dec. 31, 2023

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 Postretirement 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	)

	Currency Translation Adjustment			Pension and Other Postretirement Benefit Liability Adjustments			Total
	(In millions)
Balance at September 30, 2022, attributable to Cabot Corporation	$	(429	)	$	(10	)	$	(439	)
Other comprehensive income (loss) before reclassifications		88			—			88
Amounts reclassified from AOCI		(1	)		—			(1	)
Less: Other comprehensive income (loss) attributable to    noncontrolling interests		6			—			6
Balance at December 31, 2022, attributable to Cabot Corporation	$	(348	)	$	(10	)	$	(358	)