Financial Instruments - Offsetting of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018
Foreign exchange forward contracts
Derivative Assets
Gross Amounts Recognized	$ 1	$ 2
Gross Amounts Offset	0	0
Net Amounts Reported	1	2
Derivative Liabilities
Gross Amounts Recognized	1	0
Gross Amounts Offset	0	0
Net Amounts Reported	1	0
Cross-currency swaps
Derivative Assets
Gross Amounts Recognized	0	6
Gross Amounts Offset	0	0
Net Amounts Reported	0	6
Derivative Liabilities
Gross Amounts Recognized	5	0
Gross Amounts Offset	0	0
Net Amounts Reported	$ 5	$ 0

Fair value of liability associated with financial asset or other 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.

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Fair value, before effects of master netting arrangements, of a financial asset or other 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 assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value, after offset of derivative liability, of financial asset or other 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, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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