The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Venezuela - Additional Information (Detail) $ in Millions	12 Months Ended
Venezuela - Additional Information (Detail) $ in Millions	Sep. 30, 2017 USD ($) VEB / $	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Schedule Of Equity Method Investments [Line Items]
Operating affiliate investment	$ 15
Conversion of Bolivars to USD \| VEB / $	656
Devaluation Of Venezuelan Bolivar
Schedule Of Equity Method Investments [Line Items]
Conversion of Bolivars to USD \| VEB / $	3,345
Net gain on exchange rate devaluation	$ 1
Subsidiaries
Schedule Of Equity Method Investments [Line Items]
Cash dividends received from subsidiary	$ 4	$ 2	$ 6
Venezuela [Member] \| Carbon Black Affiliate [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	49.00%