Commitments and Contingencies (Tables)

6 Months Ended

Mar. 31, 2016

Commitments And Contingencies Disclosure [Abstract]

Schedule of Components of Purchase Commitments

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. For those commitments, the amounts included in the table below are based on market prices at March 31, 2016.

	Payments Due by Fiscal Year
	Remainder of Fiscal 2016		2017		2018		2019		2020		Thereafter		Total
	(Dollars in millions)
Reinforcement Materials	$	100	$	128	$	119	$	116	$	80	$	1,446	$	1,989
Performance Chemicals		28		51		37		32		29		154		331
Purification Solutions		5		7		1		—		—		—		13
Total	$	133	$	186	$	157	$	148	$	109	$	1,600	$	2,333