Hyperinflationary Economies - Additional Information (Detail) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / $	Sep. 30, 2019 USD ($) $ / $	Sep. 30, 2018 USD ($) $ / $
Other Nonoperating Income (Expense) [Member]
Schedule Of Equity Method Investments [Line Items]
Foreign currency transaction gain (loss)		$ (6)		$ (4)
Maximum [Member] | Other Nonoperating Income (Expense) [Member]
Schedule Of Equity Method Investments [Line Items]
Foreign currency transaction gain (loss)			$ 1
Argentina [Member]
Schedule Of Equity Method Investments [Line Items]
Percentage of net revenue		2.00%	3.00%	2.00%
Foreign currency exchange rate, translation | $ / $		76.12	57.32	39.70
Argentina [Member] | Other Nonoperating Income (Expense) [Member]
Schedule Of Equity Method Investments [Line Items]
Foreign currency transaction gain (loss)		$ (2)	$ 2	$ 3
Argentina [Member] | Maximum [Member]
Schedule Of Equity Method Investments [Line Items]
Percentage of assets and liabilities current		2.00%	2.00%
Venezuela [Member] | Carbon Black Affiliate [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	49.00%
Venezuela [Member] | Other Nonoperating Income (Expense) [Member] | Carbon Black Affiliate [Member]
Schedule Of Equity Method Investments [Line Items]
Impairment charge	$ 11
Carbon Black Operating Entity [Member] | Argentina [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		100.00%