Debt - Summary of Interest Costs and Payments (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Debt Disclosure [Abstract]
Charged to operations	$ 452	$ 398	$ 469
Capitalized	51	46	44
Total interest costs	503	444	512
Interest paid, net of amounts capitalized	$ 452	$ 390	$ 474