Fair Value Measurements and Investments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2023	Sep. 30, 2023
Assets
Investment securities	$ 7,540	$ 5,725
Level 1 \| Recurring
Assets
Total	16,673	18,483
Liabilities
Total	221	175
Level 1 \| Recurring \| Deferred compensation liability
Liabilities
Deferred compensation liability	221	175
Level 1 \| Recurring \| Derivative instruments
Liabilities
Derivative instruments	0	0
Level 1 \| Money market funds \| Recurring
Assets
Cash equivalents and restricted cash equivalents:	10,316	13,504
Other current and non-current assets:	28	23
Level 1 \| U.S. government-sponsored debt securities \| Recurring
Assets
Cash equivalents and restricted cash equivalents:	0	0
Investment securities	0	0
Level 1 \| U.S. Treasury securities \| Recurring
Assets
Cash equivalents and restricted cash equivalents:	95	301
Investment securities	5,837	4,316
Level 1 \| Marketable equity securities \| Recurring
Assets
Marketable equity securities	397	339
Level 1 \| Derivative instruments \| Recurring
Assets
Other current and non-current assets:	0	0
Level 2 \| Recurring
Assets
Total	1,762	1,401
Liabilities
Total	287	396
Level 2 \| Recurring \| Deferred compensation liability
Liabilities
Deferred compensation liability	0	0
Level 2 \| Recurring \| Derivative instruments
Liabilities
Derivative instruments	287	396
Level 2 \| Money market funds \| Recurring
Assets
Cash equivalents and restricted cash equivalents:	0	0
Other current and non-current assets:	0	0
Level 2 \| U.S. government-sponsored debt securities \| Recurring
Assets
Cash equivalents and restricted cash equivalents:	28	0
Investment securities	1,580	1,108
Level 2 \| U.S. Treasury securities \| Recurring
Assets
Cash equivalents and restricted cash equivalents:	0	0
Investment securities	0	0
Level 2 \| Marketable equity securities \| Recurring
Assets
Marketable equity securities	0	0
Level 2 \| Derivative instruments \| Recurring
Assets
Other current and non-current assets:	$ 154	$ 293

Fair value portion of accrued expenses.

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