Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
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	$ 156	$ 197
Accruals for warranties issued during the period	71	78
Accruals from acquisitions and divestitures	0	1
Accruals related to pre-existing warranties (including changes in estimates)	9	(39)
Standard Product Warranty Accrual, Decrease for Payments	(71)	(79)
Currency translation	2	(2)
Balance at end of period	$ 167	$ 156