Restructuring Costs - Schedule of Restructuring Reserve by Type of Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Restructuring Costs [Roll Forward]
Restructuring reserve, beginning balance	$ 122	$ 144
Expense	72	75	$ 132
Utilized/Paid	107	97
Restructuring reserve, ending balance	87	122	144
Severance and benefits
Restructuring Costs [Roll Forward]
Restructuring reserve, beginning balance	117	140
Expense	42	44
Utilized/Paid	74	67
Restructuring reserve, ending balance	85	117	140
Other
Restructuring Costs [Roll Forward]
Restructuring reserve, beginning balance	5	4
Expense	30	31
Utilized/Paid	33	30
Restructuring reserve, ending balance	$ 2	$ 5	$ 4