Income Taxes - Consolidated Income (Loss) Before Income Taxes and Noncontrolling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Tax Contingency [Line Items]
Income before income taxes and noncontrolling interests	$ 1,439	$ (429)	$ 2
Foreign tax authority | Ireland
Income Tax Contingency [Line Items]
Income before income taxes and noncontrolling interests	(1)	(3)	(1)
Foreign tax authority | Other Foreign
Income Tax Contingency [Line Items]
Income before income taxes and noncontrolling interests	1,684	(315)	173
U.S. Plans
Income Tax Contingency [Line Items]
Income before income taxes and noncontrolling interests	$ (244)	$ (111)	$ (170)