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Goodwill and Other Intangible Assets Goodwill Additional Information (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Goodwill [Line Items]
Goodwill impairment loss	$ 0		$ 0	$ 424	$ 0
Goodwill	$ 17,932		18,178	$ 17,932	18,178	$ 18,381
North America Retail [Member]
Goodwill [Line Items]
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount	6.00%			6.00%
Building Solutions North America
Goodwill [Line Items]
Goodwill impairment loss				$ 424
Building Solutions North America \| North America Retail [Member]
Goodwill [Line Items]
Goodwill	$ 230			230
Building Technologies & Solutions \| Global Products
Goodwill [Line Items]
Goodwill, Transfers					22
Goodwill impairment loss				0	0
Goodwill	5,579		5,547	5,579	5,547	5,593
Building Technologies & Solutions \| Building Solutions EMEA/LA
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss						47
Goodwill impairment loss				0	0
Goodwill	1,967		1,849	1,967	1,849	1,950
Building Technologies & Solutions \| Building Solutions North America
Goodwill [Line Items]
Goodwill impairment loss		$ 424		424	0
Goodwill	$ 9,160		$ 9,588	$ 9,160	$ 9,588	$ 9,603