Fair Value Measurements and Investments - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2024	Sep. 30, 2023
Assets
Investment securities	$ 6,455	$ 5,725
Level 1 | Recurring
Assets
Total	15,684	18,483
Liabilities
Total	229	175
Level 1 | Recurring | Deferred compensation liability
Liabilities
Deferred compensation liability	229	175
Level 1 | Recurring | Derivative instruments
Liabilities
Derivative instruments	0	0
Level 1 | Money market funds | Recurring
Assets
Cash equivalents and restricted cash equivalents:	9,703	13,504
Other current and non-current assets:	29	23
Level 1 | U.S. government-sponsored debt securities | Recurring
Assets
Investment securities	0	0
Level 1 | U.S. Treasury securities | Recurring
Assets
Cash equivalents and restricted cash equivalents:	7	301
Investment securities	5,659	4,316
Level 1 | Marketable equity securities | Recurring
Assets
Marketable equity securities	286	339
Level 1 | Derivative instruments | Recurring
Assets
Other current and non-current assets:	0	0
Level 2 | Recurring
Assets
Total	1,067	1,401
Liabilities
Total	263	396
Level 2 | Recurring | Deferred compensation liability
Liabilities
Deferred compensation liability	0	0
Level 2 | Recurring | Derivative instruments
Liabilities
Derivative instruments	263	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
Investment securities	789	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:	$ 278	$ 293