Income Taxes - Consolidated Income (Loss) Before Income Taxes and Noncontrolling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Income Tax Contingency [Line Items]
Income before income taxes and noncontrolling interests	$ 133	$ 295	$ 54
Foreign tax authority | Ireland
Income Tax Contingency [Line Items]
Income before income taxes and noncontrolling interests	(13)	(1)	(2)
Foreign tax authority | Other Foreign
Income Tax Contingency [Line Items]
Income before income taxes and noncontrolling interests	507	474	651
United States
Income Tax Contingency [Line Items]
Income before income taxes and noncontrolling interests	$ (361)	$ (178)	$ (595)