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, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 0	$ 158	$ 99	$ 78	$ 158	$ 177
2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs								$ 288
Committed restructuring liabilities assumed from Tyco Merger [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	56							78
Restructuring Reserve, Settled without Cash							$ (22)
2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs								620
Payments for Restructuring					(16)		(88)	(32)
Restructuring Reserve, Settled without Cash							1	(221)
Adjustment to restructuring reserves							(25)
Restructuring Reserve	76				76		92	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							(22)
Employee Severance | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs								368
Payments for Restructuring					(14)		(86)	(32)
Restructuring Reserve, Settled without Cash							0	0
Adjustment to restructuring reserves							(25)
Restructuring Reserve	70				70		84	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	0
Restructuring Reserve, Settled without Cash							0	(190)
Adjustment to restructuring reserves							0
Restructuring Reserve	0				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)		(2)	0
Restructuring Reserve, Settled without Cash							0	(32)
Adjustment to restructuring reserves							0
Restructuring Reserve	4				4		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	0
Restructuring Reserve, Settled without Cash							1	1
Adjustment to restructuring reserves							0
Restructuring Reserve	$ 2				$ 2		2	1
Building Solutions EMEA/LA | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs								17
Corporate Segment | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs								161
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
Adient | Discontinued Operations | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs								$ 332