Income Taxes - (Loss) Income Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Domestic	$ (346)	$ 362	$ 647
Foreign	(1,491)	1,025	1,342
(Loss) income before income taxes	$ (1,837)	$ 1,387	$ 1,989