Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash flow hedges	$ (18)	$ (3)
Interest Rate Swap \| Cash flow hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash flow hedges	$ (19)

Amount, after tax and reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness, attributable to parent.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-11

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Balance Type:	credit
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