Significant Restructuring Costs Change in Restructuring Reserve - 2018 Restructuring Plan (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 62	$ 0	$ 173	$ 0
2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						$ 263
Payments for Restructuring			(21)		$ (67)	(47)
Restructuring Reserve, Settled without Cash			1		(1)	(42)
Restructuring Reserve	78		78		102	174
Employee Severance | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						209
Payments for Restructuring			(21)		(61)	(45)
Restructuring Reserve, Settled without Cash			0		0	0
Restructuring Reserve	78		78		99	164
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		0	(42)
Restructuring Reserve	0		0		0	0
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	0
Restructuring Reserve	0		0		4	10
Currency Translation | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						0
Payments for Restructuring			0		0	0
Restructuring Reserve, Settled without Cash			1		(1)	0
Restructuring Reserve	$ 0		0		(1)	0
Global Products | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						113
Building Solutions EMEA/LA | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						56
Corporate Segment | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						50
Building Solutions Asia Pacific | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						16
Building Solutions North America | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						20
Continuing Operations | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						255
Discontinued Operations | Power Solutions | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						$ 8
Transfer To Held for Sale [Member] | Power Solutions | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					(4)
Transfer To Held for Sale [Member] | Power Solutions | Employee Severance | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					(4)
Transfer To Held for Sale [Member] | Power Solutions | Long-Lived Asset Impairment | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					0
Transfer To Held for Sale [Member] | Power Solutions | Other Restructuring | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					0
Transfer To Held for Sale [Member] | Power Solutions | Currency Translation | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash					$ 0
Adoption of ASC 842 | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Adoption of ASC 842			(4)
Adoption of ASC 842 | Employee Severance | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Adoption of ASC 842			0
Adoption of ASC 842 | Long-Lived Asset Impairment | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Adoption of ASC 842			0
Adoption of ASC 842 | Other Restructuring | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Adoption of ASC 842			(4)
Adoption of ASC 842 | Currency Translation | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Adoption of ASC 842			$ 0