Significant Restructuring Costs Change in Restructuring Reserve - 2017 Restructuring Plan (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 610	$ 235	$ 783	$ 235
2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							$ 367
Payments for Restructuring			(35)		$ (13)	$ (158)	(75)
Restructuring Reserve, Settled without Cash					(3)	(1)	(78)
Adjustment to restructuring reserves							25
Restructuring Reserve	21		21		61	80	239
2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						263
Payments for Restructuring			(30)		(67)	(47)
Restructuring Reserve, Settled without Cash					(1)	(42)
Currency Translation			(1)
Restructuring Reserve	69		69		102	174
Employee Severance | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							276
Payments for Restructuring			(35)		(11)	(152)	(75)
Restructuring Reserve, Settled without Cash					0	0	0
Adjustment to restructuring reserves							25
Restructuring Reserve	25		25		60	74	226
Employee Severance | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						209
Payments for Restructuring			(30)		(61)	(45)
Restructuring Reserve, Settled without Cash					0	0
Restructuring Reserve	69		69		99	164
Long-Lived Asset Impairment | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							77
Payments for Restructuring			0		0	0	0
Restructuring Reserve, Settled without Cash					0	0	(77)
Adjustment to restructuring reserves							0
Restructuring Reserve	0		0		0	0	0
Long-Lived Asset Impairment | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						42
Payments for Restructuring			0		0	0
Restructuring Reserve, Settled without Cash					0	(42)
Restructuring Reserve	0		0		0	0
Other Restructuring | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							14
Payments for Restructuring			0		(2)	(6)	0
Restructuring Reserve, Settled without Cash					0	0	(1)
Adjustment to restructuring reserves							0
Restructuring Reserve	0		0		5	7	13
Other Restructuring | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						12
Payments for Restructuring			0		(6)	(2)
Restructuring Reserve, Settled without Cash					0	0
Restructuring Reserve	0		0		4	10
Currency Translation | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							0
Currency Translation					3	1	0
Adjustment to restructuring reserves							0
Restructuring reserve, CTA balance	(4)		(4)		(4)	(1)	0
Currency Translation | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						0
Payments for Restructuring			0		0	0
Currency Translation			(1)		1	0
Restructuring reserve, CTA balance	$ 0		0		(1)	0
Corporate Segment | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							166
Corporate Segment | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						50
Building Technologies & Solutions EMEA LA [Member] | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							74
Building Solutions North America | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							59
Building Solutions North America | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						20
Building Solutions Asia Pacific | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							16
Building Solutions Asia Pacific | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						16
Global Products | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							32
Global Products | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						113
Continuing Operations | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							347
Continuing Operations | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						255
Power Solutions | Transfer To Held for Sale [Member] | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					(3)
Power Solutions | Transfer To Held for Sale [Member] | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					(4)
Power Solutions | Transfer To Held for Sale [Member] | Employee Severance | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					(3)
Power Solutions | Transfer To Held for Sale [Member] | Employee Severance | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					(4)
Power Solutions | Transfer To Held for Sale [Member] | Long-Lived Asset Impairment | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					0
Power Solutions | Transfer To Held for Sale [Member] | Long-Lived Asset Impairment | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					0
Power Solutions | Transfer To Held for Sale [Member] | Other Restructuring | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					0
Power Solutions | Transfer To Held for Sale [Member] | Other Restructuring | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					0
Power Solutions | Transfer To Held for Sale [Member] | Currency Translation | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					0
Power Solutions | Transfer To Held for Sale [Member] | Currency Translation | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					$ 0
Power Solutions | Discontinued Operations | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs							$ 20
Power Solutions | Discontinued Operations | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						$ 8
Adoption of ASC 842 | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			(5)
Adoption of ASC 842 | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			4
Adoption of ASC 842 | Employee Severance | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			0
Adoption of ASC 842 | Employee Severance | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			0
Adoption of ASC 842 | Long-Lived Asset Impairment | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			0
Adoption of ASC 842 | Long-Lived Asset Impairment | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			0
Adoption of ASC 842 | Other Restructuring | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			(5)
Adoption of ASC 842 | Other Restructuring | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			4
Adoption of ASC 842 | Currency Translation | 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			0
Adoption of ASC 842 | Currency Translation | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Translation and Other Adjustment			$ 0