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Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Goodwill [Roll Forward]
Beginning Balance		$ 18,178
Business Acquisitions		42
Goodwill, Impairment Loss		(424)
Currency Translation and Other		(37)
Ending Balance	$ 17,759	17,759
Building Solutions North America
Goodwill [Roll Forward]
Beginning Balance		9,588
Business Acquisitions		0
Goodwill, Impairment Loss	(424)	(424)
Currency Translation and Other		(20)
Ending Balance	9,144	9,144
Building Solutions EMEA/LA
Goodwill [Roll Forward]
Beginning Balance		1,849
Business Acquisitions		23
Business Divestitures			$ (1)
Goodwill, Impairment Loss		0
Currency Translation and Other		3
Ending Balance	1,875	1,875
Building Solutions Asia Pacific
Goodwill [Roll Forward]
Beginning Balance		1,194
Business Acquisitions		0
Goodwill, Impairment Loss		0
Currency Translation and Other		10
Ending Balance	1,204	1,204
Global Products
Goodwill [Roll Forward]
Beginning Balance		5,547
Business Acquisitions		19
Goodwill, Impairment Loss		0
Currency Translation and Other		(30)
Ending Balance	$ 5,536	$ 5,536