Venezuela	6 Months Ended
Mar. 31, 2017
Equity Method Investments And Joint Ventures [Abstract]
Venezuela	M. Venezuela Cabot owns 49% of an operating carbon black affiliate in Venezuela, which is accounted for as an equity affiliate, through wholly-owned subsidiaries that carry the investment and receive its dividends. As of March 31, 2017, these subsidiaries carried the operating affiliate investment of $13 million. During each of the six month periods ended March 31, 2017 and 2016, the Company received dividends in the amounts of $2 million, which were paid in U.S. dollars. A significant portion of the Company’s operating affiliate’s sales are exports denominated in U.S. dollars. The Venezuelan government mandates that a certain percentage of the dollars collected from these sales be converted into bolivars. The exchange rate made available to the Company as of March 31, 2017 was 709 bolivars to the U.S. dollar. The operating affiliate and the Company’s wholly-owned subsidiaries remeasured their bolivar denominated monetary accounts to reflect the current rate. The operating entity has generally been profitable. The Company continues to closely monitor developments in Venezuela and their potential impact on the recoverability of its equity affiliate investment. Any future change in the exchange rate made available to the Company or opening of additional parallel markets could cause the Company to change the exchange rate it uses and result in gains or losses on the bolivar denominated assets held by its operating affiliate and wholly-owned subsidiaries.

Venezuela

6 Months Ended

Mar. 31, 2017

Equity Method Investments And Joint Ventures [Abstract]

M. Venezuela

Cabot owns 49% of an operating carbon black affiliate in Venezuela, which is accounted for as an equity affiliate, through wholly-owned subsidiaries that carry the investment and receive its dividends. As of March 31, 2017, these subsidiaries carried the operating affiliate investment of $13 million.

During each of the six month periods ended March 31, 2017 and 2016, the Company received dividends in the amounts of $2 million, which were paid in U.S. dollars.

A significant portion of the Company’s operating affiliate’s sales are exports denominated in U.S. dollars. The Venezuelan government mandates that a certain percentage of the dollars collected from these sales be converted into bolivars. The exchange rate made available to the Company as of March 31, 2017 was 709 bolivars to the U.S. dollar. The operating affiliate and the Company’s wholly-owned subsidiaries remeasured their bolivar denominated monetary accounts to reflect the current rate.

The operating entity has generally been profitable. The Company continues to closely monitor developments in Venezuela and their potential impact on the recoverability of its equity affiliate investment. Any future change in the exchange rate made available to the Company or opening of additional parallel markets could cause the Company to change the exchange rate it uses and result in gains or losses on the bolivar denominated assets held by its operating affiliate and wholly-owned subsidiaries.