Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash flow hedges	$ 12	$ 37	$ 4	$ 74
Interest Rate Swap | Cash flow hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash flow hedges		37		77
Derivative Notional Amount Terminated		500		500
Terminated Interest Rate Swap | Cash flow hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cash flow hedges		$ 41		$ 41