Short-Term and Long-Term Debt - Schedule of Carrying Values and Estimated Fair Values of Long term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2026	Sep. 30, 2025
Debt Instrument [Line Items]
Current portion of long-term debt, carrying value	$ 2	$ 2
Long-term debt, carrying value	2,571	2,614
Carrying Value
Debt Instrument [Line Items]
Current portion of long-term debt, carrying value	2	2
Long-term debt, carrying value	2,571	2,614
Fair Value
Debt Instrument [Line Items]
Current portion of long-term debt, fair value	2	2
Long-term debt, fair value	$ 2,258	$ 2,350

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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