Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Guarantor Obligations [Line Items]
Maximum length, in years, of a product warranty for it to be recorded in other current liabilities	1 year
Minimum length, in years, of a product warranty for it to be recorded in other noncurrent liabilities	1 year
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 167	$ 156
Accruals for warranties issued during the period	91	71
Accruals related to pre-existing warranties (including changes in estimates)	11	9
Standard Product Warranty Accrual, Decrease for Payments	(77)	(71)
Currency translation	0	2
Balance at end of period	$ 192	$ 167