Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as current. 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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Name:	us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents (Details) - USD ($) $ in Millions	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 18,034	$ 16,289
Cash, cash equivalents, restricted cash and restricted cash equivalents	21,274	19,171	$ 16,934	$ 10,832
U.S. litigation escrow
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and restricted cash equivalents	894	901
Customer collateral
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and restricted cash equivalents	2,221	1,850
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and restricted cash equivalents	$ 125	$ 131