Guarantees (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2016
Guarantor Obligations [Line Items]
Document Period End Date		Sep. 30, 2019
Insurance Settlements Receivable, Current		$ 5	$ 6
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
Post sale contingent tax indemnification liabilities			255	$ 290
Insurance Settlements Receivable, Noncurrent		$ 18	20
Release of tax indemnification reserve	$ (226)	(226)
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period		315	323
Accruals for warranties issued during the period		110	128
Accruals from acquisitions and divestitures (1)		1	0
Accruals related to pre-existing warranties (including changes in estimates)		(39)	(14)
Settlements made (in cash or in kind) during the period		(101)	(120)
Currency translation		(1)	(2)
Balance at end of period		$ 285	315
Business Divestitures, Not Specific
Guarantor Obligations [Line Items]
Post sale contingent tax indemnification liabilities			$ 235