Fair Value Measurements and Investments - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2025	Sep. 30, 2024
Assets
Investment securities	$ 3,180	$ 5,451
Level 1 \| Fair Value, Measurements, Recurring
Assets
Total	12,654	15,684
Liabilities
Total	235	238
Level 1 \| Fair Value, Measurements, Recurring \| Deferred compensation liability
Liabilities
Deferred compensation liability	235	238
Level 1 \| Fair Value, Measurements, Recurring \| Derivative instruments
Liabilities
Derivative instruments	0	0
Level 1 \| Money market funds \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	9,438	10,403
Other current and non-current assets:	27	25
Level 1 \| U.S. Treasury securities \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	7	7
Investment securities	2,868	4,948
Level 1 \| Marketable equity securities \| Fair Value, Measurements, Recurring
Assets
Marketable equity securities	314	301
Level 1 \| U.S. government-sponsored debt securities \| Fair Value, Measurements, Recurring
Assets
Investment securities	0	0
Level 1 \| Derivative instruments \| Fair Value, Measurements, Recurring
Assets
Other current and non-current assets:	0	0
Level 2 \| Fair Value, Measurements, Recurring
Assets
Total	499	599
Liabilities
Total	252	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	252	226
Level 2 \| Money market funds \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	0	0
Other current and non-current assets:	0	0
Level 2 \| U.S. Treasury securities \| Fair Value, Measurements, Recurring
Assets
Cash equivalents and restricted cash equivalents:	0	0
Investment securities	0	0
Level 2 \| Marketable equity securities \| Fair Value, Measurements, Recurring
Assets
Marketable equity securities	0	0
Level 2 \| U.S. government-sponsored debt securities \| Fair Value, Measurements, Recurring
Assets
Investment securities	305	496
Level 2 \| Derivative instruments \| Fair Value, Measurements, Recurring
Assets
Other current and non-current assets:	$ 194	$ 103

Fair value portion of accrued expenses.

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