Income Taxes - Summary of Gross Amounts of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Unrecognized Tax Benefits [Roll Forward]
Balance at October 1	$ 269	$ 267	$ 354
Increase due to acquisitions	0	0	2
Increase due to current year tax positions	22	22	40
Increase due to prior year tax positions	0	33	60
Decreases due to prior year tax positions	0	(29)	0
Decrease due to settlements with tax authorities	(64)	(6)	(77)
Decrease due to lapse of statute of limitations	(6)	(18)	(112)
Balance at September 30	221	269	267
Unrecognized tax benefits that would affect the effective tax rate if recognized	$ 257	$ 366	$ 348

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

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Amount of decrease 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 settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from acquisitions.

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

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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