Guarantees (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016
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
Post sale contingent tax indemnification liabilities		$ 290	$ 290
Tax indemnification liabilities related to other divestitures		11
Warranties transferred to liabilities held for sale		13
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period		374	288
Accruals for warranties issued during the period		312	314
Accruals from acquisitions and divestitures (1)	[1]	7	83
Accruals related to pre-existing warranties (including changes in estimates)		(4)	(17)
Settlements made (in cash or in kind) during the period		(280)	(297)
Currency translation		0	3
Balance at end of period		409	$ 374
Business Divestitures, Not Specific
Guarantor Obligations [Line Items]
Post sale contingent tax indemnification liabilities		$ 255

[1] The year ended September 30, 2017 includes $13 million of product warranties transferred to liabilities held for sale on the consolidated statements of financial position. Refer to Note 4, "Discontinued Operations," of the notes to consolidated financial statements for further information regarding the Company's disposal groups classified as held for sale.