Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits, beginning	$ 167	$ 209
Additions for current year tax positions	78	24
Additions for prior year tax positions	13	9
Reductions for prior year tax positions	(10)	(65)
Acquisitions and divestitures	0	1
Reductions for settlements with tax authorities	(5)	0
Reductions for expiration of statutes of limitations	(8)	(11)
Unrecognized tax benefits, ending	$ 235	$ 167