Significant Restructuring Costs Change in Restructuring Reserve - 2016 Restructuring Plan (Details) - USD ($) $ in Millions	3 Months Ended					9 Months Ended		12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 0	$ 158	$ 49	$ 99	$ 78	$ 158	$ 226
2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									$ 288
2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									620
Restructuring Reserve	74					74		$ 92	445
Payments for Restructuring						(18)		(88)	(32)
Restructuring Reserve, Settled without Cash								1	(221)
Adjustment to restructuring reserves								(25)
Employee Severance | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									368
Restructuring Reserve	68					68		84	414
Payments for Restructuring						(16)		(86)	(32)
Restructuring Reserve, Settled without Cash								0	0
Adjustment to restructuring reserves								(25)
Fixed Asset Impairment | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									190
Restructuring Reserve	0					0		0	0
Payments for Restructuring						0		0	0
Restructuring Reserve, Settled without Cash								0	(190)
Adjustment to restructuring reserves								0
Other Restructuring | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									62
Restructuring Reserve	4					4		6	30
Payments for Restructuring						(2)		(2)	0
Restructuring Reserve, Settled without Cash								0	(32)
Adjustment to restructuring reserves								0
Currency Translation | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									0
Restructuring Reserve	2					2		2	1
Payments for Restructuring						0		0	0
Restructuring Reserve, Settled without Cash								1	1
Adjustment to restructuring reserves								0
Tyco merger [Member] | 2016 Restructuring Plan [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									78
Restructuring Reserve	$ 56					$ 56
Restructuring Reserve, Settled without Cash								(22)
Tyco merger [Member] | Employee Severance | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									78
Restructuring Reserve, Settled without Cash								(22)
Tyco merger [Member] | Fixed Asset Impairment | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									0
Restructuring Reserve, Settled without Cash								0
Tyco merger [Member] | Other Restructuring | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									0
Restructuring Reserve, Settled without Cash								0
Tyco merger [Member] | Currency Translation | 2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs									0
Restructuring Reserve, Settled without Cash								0
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