Concentration of Credit Risk (Tables)

12 Months Ended

Sep. 30, 2015

Risks And Uncertainties [Abstract]

Schedule of Account Receivable

Tire manufacturers comprise a significant portion of Cabot’s trade receivable balance. The accounts receivable balance for these significant customers as a group is as follows:

	September 30
	2015		2014
	(Dollars in millions)
Tire manufacturers	$	217	$	311