Financial Instruments and Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Institutional money market investments	$ 200	$ 1,549
Fair value of debt classified from long term to short term	503	702
Fair value of long-term debt	18,537	18,970
Remaining cash equivalents	$ 2,083	$ 1,276

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes 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.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant