Commitments and Contingencies (Tables)

12 Months Ended

Sep. 30, 2017

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 Ended September 30	(In millions)
2018	$	25
2019		16
2020		10
2021		9
2022		8
2023 and thereafter		68
Total future minimum rental commitments	$	136

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 2017, 2016 and 2015 are as follows:

	Years Ended September 30
	2017		2016		2015
	(In millions)
Reinforcement Materials	$	281	$	193	$	276
Performance Chemicals		43		68		62
Purification Solutions		7		7		14
Total	$	331	$	268	$	352

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, 2017 which may differ from actual market prices at the time of purchase.

	Payments Due by Fiscal Year
	2018		2019		2020		2021		2022		Thereafter		Total
	(In millions)
Reinforcement Materials	$	253	$	250	$	148	$	108	$	108	$	1,487	$	2,354
Performance Chemicals		41		41		39		37		26		371		555
Purification Solutions		10		7		6		1		—		—		24
Total	$	304	$	298	$	193	$	146	$	134	$	1,858	$	2,933