Fair Value Measurements and Investments - Schedule of Assets and Liabilities Measured (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Assets
Investment securities	$ 2,421	$ 5,451
Level 1 \| Fair Value, Measurements, Recurring
Assets
Total	16,315	15,684
Liabilities
Total	268	238
Level 1 \| Fair Value, Measurements, Recurring \| Deferred compensation liability
Liabilities
Deferred compensation liability	268	238
Level 1 \| Fair Value, Measurements, Recurring \| Derivative instruments
Liabilities
Derivative instruments	0	0
Level 2 \| Fair Value, Measurements, Recurring
Assets
Total	367	599
Liabilities
Total	319	226
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	319	226
Money market funds \| Level 1 \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	13,760	10,403
Other current and non-current assets:	28	25
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:	0	7
Investment securities	2,116	4,948
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	411	301
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	305	496
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:	$ 62	$ 103

Fair value portion of accrued expenses.

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