Commitments and Contingencies (Tables)

12 Months Ended

Sep. 30, 2018

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Rental Commitments under Non-Cancelable Leases

Future minimum rental commitments under non-cancelable leases are as follows:

Years Ending September 30	(In millions)
2019	$	22
2020		13
2021		10
2022		9
2023		9
2024 and thereafter		69
Total future minimum rental commitments	$	132

Schedule of Raw Material Purchased under Long Term Purchase Agreements

Cabot has entered into long-term purchase agreements primarily for the purchase of raw materials. Under certain of these agreements, the quantity of material being purchased is fixed, but the price paid changes as market prices change. Raw materials purchased under these agreements by segment for fiscal 2018, 2017 and 2016 are as follows:

	Years Ended September 30
	2018		2017		2016
	(In millions)
Reinforcement Materials	$	375	$	281	$	193
Performance Chemicals		55		43		68
Purification Solutions		11		7		7
Specialty Fluids		—		—		—
Total	$	441	$	331	$	268

Schedule of Components of Purchase Commitments

For these purchase commitments, the amounts included in the table below are based on market prices as of September 30, 2018 which may differ from actual market prices at the time of purchase.

	Payments Due by Fiscal Year
	2019		2020		2021		2022		2023		Thereafter		Total
	(In millions)
Reinforcement Materials	$	361	$	234	$	142	$	138	$	131	$	1,703	$	2,709
Performance Chemicals		70		58		57		57		33		465		740
Purification Solutions		8		5		1		—		—		—		14
Specialty Fluids		15		—		—		—		—		—		15
Total	$	454	$	297	$	200	$	195	$	164	$	2,168	$	3,478