Product Warranties (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Product Warranties Disclosures [Abstract]
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	$ 300	$ 319
Accruals for warranties issued during the period	324	280
Accruals from acquisitions and divestitures	51	0
Accruals related to pre-existing warranties (including changes in estimates)	(13)	(11)
Settlements made (in cash or in kind) during the period	(301)	(282)
Currency translation	4	(6)
Balance at end of period	$ 365	$ 300