Income Taxes - Income Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Domestic	$ 647	$ 424	$ 330
Foreign	1,342	243	71
Income before income taxes	$ 1,989	$ 667	$ 401