Income Taxes - Schedule of Reconciliation of Beginning and Ending Unrecognized Tax Benefits by Fiscal Year (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Unrecognized Tax Benefits [Roll Forward]
Balance as of beginning of period	$ 3,750	$ 3,497	$ 2,683
Increase related to prior years	281	148	515
Decrease related to prior years	(2,455)	(322)	(190)
Increase related to current year	150	556	510
Decrease related to settlements with taxing authorities	(49)	(127)	(17)
Decrease related to lapsing statute of limitations	(5)	(2)	(4)
Balance as of end of period	$ 1,672	$ 3,750	$ 3,497

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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