Goodwill and Other Intangible Assets Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 18,178	$ 17,932	$ 18,178
Business Acquisitions		300	56
Business Divestitures		(7)	(11)
Impairments		0	(424)
Currency Translation and Other		110	133
Goodwill, Ending Balance		18,335	17,932
Building Solutions North America
Goodwill [Roll Forward]
Impairments			(424)
Building Solutions North America \| Building Technologies & Solutions
Goodwill [Roll Forward]
Goodwill, Beginning Balance	9,588	9,160	9,588
Business Acquisitions		21	0
Business Divestitures		0	0
Impairments	(424)	0	(424)
Currency Translation and Other		34	(4)
Goodwill, Ending Balance		9,215	9,160
Building Solutions EMEA/LA \| Building Technologies & Solutions
Goodwill [Roll Forward]
Goodwill, Beginning Balance	1,849	1,967	1,849
Business Acquisitions		35	35
Business Divestitures		0	0
Impairments		0	0
Currency Translation and Other		19	83
Goodwill, Ending Balance		2,021	1,967
Building Solutions Asia Pacific \| Building Technologies & Solutions
Goodwill [Roll Forward]
Goodwill, Beginning Balance	1,194	1,226	1,194
Business Acquisitions		0	0
Business Divestitures		(7)	(11)
Impairments		0	0
Currency Translation and Other		21	43
Goodwill, Ending Balance		1,240	1,226
Global Products \| Building Technologies & Solutions
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 5,547	5,579	5,547
Business Acquisitions		244	21
Business Divestitures		0	0
Impairments		0	0
Currency Translation and Other		36	11
Goodwill, Ending Balance		$ 5,859	$ 5,579

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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