Fair Value Measurements and Investments - Schedule of Assets and Liabilities Measured (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Assets
Investment securities	$ 5,451	$ 5,725
Level 1 \| Fair Value, Measurements, Recurring
Assets
Total	15,684	18,483
Liabilities
Total	238	175
Level 1 \| Fair Value, Measurements, Recurring \| Deferred compensation liability
Liabilities
Deferred compensation liability	238	175
Level 1 \| Fair Value, Measurements, Recurring \| Derivative instruments
Liabilities
Derivative instruments	0	0
Level 2 \| Fair Value, Measurements, Recurring
Assets
Total	599	1,401
Liabilities
Total	226	396
Level 2 \| Fair Value, Measurements, Recurring \| Deferred compensation liability
Liabilities
Deferred compensation liability	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Derivative instruments
Liabilities
Derivative instruments	226	396
Money market funds \| Level 1 \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	10,403	13,504
Other current and non-current assets:	25	23
Money market funds \| Level 2 \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	0	0
Other current and non-current assets:	0	0
U.S. Treasury securities \| Level 1 \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	7	301
Investment securities	4,948	4,316
U.S. Treasury securities \| Level 2 \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	0	0
Investment securities	0	0
Marketable equity securities \| Level 1 \| Fair Value, Measurements, Recurring
Assets
Marketable equity securities	301	339
Marketable equity securities \| Level 2 \| Fair Value, Measurements, Recurring
Assets
Marketable equity securities	0	0
U.S. government-sponsored debt securities \| Level 1 \| Fair Value, Measurements, Recurring
Assets
Investment securities	0	0
U.S. government-sponsored debt securities \| Level 2 \| Fair Value, Measurements, Recurring
Assets
Investment securities	496	1,108
Derivative instruments \| Level 1 \| Fair Value, Measurements, Recurring
Assets
Other current and non-current assets:	0	0
Derivative instruments \| Level 2 \| Fair Value, Measurements, Recurring
Assets
Other current and non-current assets:	$ 103	$ 293

Fair value portion of accrued expenses.

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