Financial Statements - Additional Information (Detail) $ in Millions	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)
Financial Statement Details [Line Items]
Number of Countries in which Entity Operates	150
Interest percentage minimum for investments in partially-owned affiliates to be accounted for by the equity method	20.00%
Restricted Cash and Cash Equivalents	$ 19	$ 15
Restricted Cash and Investments, Current		6
Restricted Cash and Cash Equivalents, Noncurrent		$ 9

Financial Statement Details [Line Items]

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Interest percentage minimum for investments in partially-owned affiliates to be accounted for by the equity method.

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The number of countries in which the entity operates as of balance sheet date.

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Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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The current cash, cash equivalents and investments that are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes current cash equivalents and investments that are similarly restricted as to withdrawal, usage or disposal.

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