Merger Transaction (Details) - USD ($) $ in Millions		12 Months Ended
	Sep. 02, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, purchase accounting adjustments			$ (258)
Cash and cash equivalents	$ 489
Accounts receivable	2,034
Inventories	807
Other current assets	617
Property, plant, and equipment	1,216
Goodwill, acquired during period		$ 15	$ (256)
Intangible assets - net	6,384
Other noncurrent assets	536
Total assets required	28,188
Short term debt	462
Accounts payable	725
Accrued compensation and benefits	312
Other current liabilities	1,481
Long-term debt	6,416
Long-term deferred tax liabilities	718
Long-term pension and postretirement benefits	774
Other noncurrent liabilities	1,456
Total liabilities acquired	12,344
Noncontrolling interests	37
Net assets acquired	15,807
Cash consideration paid to JCI Inc. shareholders	3,864			$ 3,864
Total fair value of consideration transferred	19,671			$ 19,700
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 2,280
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	12 years
Technology-Based Intangible Assets [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 1,650
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	11 years
Other Finite Lived Intangible [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired	$ 214
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years
Indefinite-lived trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets Acquired	$ 2,080
Other indefinite-lived intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets Acquired	90
In-process research and development
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets Acquired	70
Tyco merger [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, acquired during period	$ 16,105