Derivative Financial Instruments - Summary of Amounts Recorded in Consolidated Balance Sheets Footnote (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts in asset	$ 8
Foreign exchange derivative contracts in liability	5
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts in asset		$ 2
Foreign exchange derivative contracts in liability	$ 36	$ 13

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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