Significant Restructuring Costs Change in Restructuring Reserve - 2016 Restructuring Plan (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 99	$ 78	$ 60	$ 177	$ 60
Committed restructuring liabilities assumed from Tyco Merger [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						$ 78
Restructuring Reserve, Settled without Cash				(4)
2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						620
Payments for Restructuring				(51)		(32)
Restructuring Reserve, Settled without Cash				(3)		(221)
Restructuring Reserve	168			168		445
Employee Severance | Committed restructuring liabilities assumed from Tyco Merger [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						78
Restructuring Reserve, Settled without Cash				(4)
Employee Severance | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						368
Payments for Restructuring				(49)		(32)
Restructuring Reserve, Settled without Cash				0		0
Restructuring Reserve	164			164		414
Fixed Asset Impairment | Committed restructuring liabilities assumed from Tyco Merger [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						0
Restructuring Reserve, Settled without Cash				0
Fixed Asset Impairment | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						190
Payments for Restructuring				0		0
Restructuring Reserve, Settled without Cash				0		(190)
Restructuring Reserve	0			0		0
Other Restructuring | Committed restructuring liabilities assumed from Tyco Merger [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						0
Restructuring Reserve, Settled without Cash				0
Other Restructuring | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						62
Payments for Restructuring				(2)		0
Restructuring Reserve, Settled without Cash				0		(32)
Restructuring Reserve	6			6		30
Currency Translation | Committed restructuring liabilities assumed from Tyco Merger [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						0
Restructuring Reserve, Settled without Cash				0
Currency Translation | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						0
Payments for Restructuring				0		0
Restructuring Reserve, Settled without Cash				(3)		1
Restructuring Reserve	$ (2)			(2)		1
Continuing Operations | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						288
Continuing Operations | Building Efficiency Systems and Service North America | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						2
Continuing Operations | Building Efficiency Asia | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						26
Continuing Operations | Building Efficiency Rest of World [Member] | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						16
Continuing Operations | Building Efficiency Products North America | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						9
Continuing Operations | Building Technologies & Solutions Tyco [Member] | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						8
Continuing Operations | Corporate Segment | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						161
Continuing Operations | Buildings Tyco [Member] | Committed restructuring liabilities assumed from Tyco Merger [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						74
Continuing Operations | Power Solutions | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						66
Adient spin-off [Member] | Transfer To Held for Sale [Member] | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				(216)
Adient spin-off [Member] | Transfer To Held for Sale [Member] | Employee Severance | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				(194)
Adient spin-off [Member] | Transfer To Held for Sale [Member] | Fixed Asset Impairment | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				0
Adient spin-off [Member] | Transfer To Held for Sale [Member] | Other Restructuring | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				(22)
Adient spin-off [Member] | Transfer To Held for Sale [Member] | Currency Translation | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				0
Scott Safety business [Member] | Transfer To Held for Sale [Member] | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				(3)
Scott Safety business [Member] | Transfer To Held for Sale [Member] | Employee Severance | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				(3)
Scott Safety business [Member] | Transfer To Held for Sale [Member] | Fixed Asset Impairment | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				0
Scott Safety business [Member] | Transfer To Held for Sale [Member] | Other Restructuring | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				0
Scott Safety business [Member] | Transfer To Held for Sale [Member] | Currency Translation | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Settled without Cash				$ 0
Automotive Experience | Discontinued Operations | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs						$ 332