Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details) $ in Millions	3 Months Ended
Dec. 31, 2019 USD ($)
Goodwill [Roll Forward]
Beginning Balance	$ 18,178
Business Acquisitions	29
Currency Translation and Other	144
Ending Balance	18,351
Building Technologies & Solutions \| Building Solutions North America
Goodwill [Roll Forward]
Beginning Balance	9,588
Business Acquisitions	0
Currency Translation and Other	12
Ending Balance	9,600
Building Technologies & Solutions \| Building Solutions EMEA/LA
Goodwill [Roll Forward]
Beginning Balance	1,849
Business Acquisitions	12
Currency Translation and Other	67
Ending Balance	1,928
Building Technologies & Solutions \| Building Solutions Asia Pacific
Goodwill [Roll Forward]
Beginning Balance	1,194
Business Acquisitions	0
Currency Translation and Other	36
Ending Balance	1,230
Building Technologies & Solutions \| Global Products
Goodwill [Roll Forward]
Beginning Balance	5,547
Business Acquisitions	17
Currency Translation and Other	29
Ending Balance	$ 5,593

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
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-Paragraph 1
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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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