Commitments and Contingencies (Tables)

3 Months Ended

Dec. 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 December 31, 2016.

	Payments Due by Fiscal Year
	Remainder of Fiscal 2017		2018		2019		2020		2021		Thereafter		Total
	(Dollars in millions)
Reinforcement Materials	$	154	$	189	$	184	$	118	$	91	$	1,202	$	1,938
Performance Chemicals		34		43		30		23		21		109		260
Purification Solutions		7		8		6		6		—		—		27
Total	$	195	$	240	$	220	$	147	$	112	$	1,311	$	2,225