Significant Restructuring and Impairment Costs (Detail) $ in Millions	12 Months Ended			24 Months Ended
	Sep. 30, 2017 USD ($) Plant Employees	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2017 USD ($) Plant Employees
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve		$ 445
Restructuring and impairment costs	$ 367	288	$ 215
Number of employees to be severed | Employees				6,100
Restructuring and Related Cost, Number of Positions Eliminated, Inception to Date | Employees	1,600			1,600
Restructuring And Related Cost Expected Number Of Plants To Be Closed | Plant	10
Number Of Plants Closed | Plant	4			4
Power Solutions
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ (20)	(66)	(11)
Number of employees to be severed | Employees				100
Adient
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		332	$ 182
2017 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	239			$ 239
Adjustment to restructuring reserves	25
Restructuring and impairment costs	367
Payments for Restructuring	(75)
Restructuring Reserve, Settled without Cash	(78)
2017 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	367
2017 Restructuring Plan [Member] | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	226			226
Adjustment to restructuring reserves	25
Restructuring and impairment costs	276
Payments for Restructuring	(75)
Restructuring Reserve, Settled without Cash	0
2017 Restructuring Plan [Member] | Fixed Asset Impairment
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	0			0
Adjustment to restructuring reserves	0
Restructuring and impairment costs	77
Payments for Restructuring	0
Restructuring Reserve, Settled without Cash	(77)
2017 Restructuring Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	13			13
Adjustment to restructuring reserves	0
Restructuring and impairment costs	14
Payments for Restructuring	0
Restructuring Reserve, Settled without Cash	(1)
2017 Restructuring Plan [Member] | Currency Translation
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	0			0
Adjustment to restructuring reserves	0
Restructuring and impairment costs	0
Payments for Restructuring	0
Restructuring Reserve, Settled without Cash	0
2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	92			92
Adjustment to restructuring reserves	(25)
Restructuring and impairment costs		620
Payments for Restructuring	(88)	(32)
Restructuring Reserve, Settled without Cash	1	(221)
2016 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		288
2016 Restructuring Plan [Member] | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	84	414		84
Adjustment to restructuring reserves	(25)
Restructuring and impairment costs		368
Payments for Restructuring	(86)	(32)
Restructuring Reserve, Settled without Cash	0	0
2016 Restructuring Plan [Member] | Fixed Asset Impairment
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	0	0		0
Adjustment to restructuring reserves	0
Restructuring and impairment costs		190
Payments for Restructuring	0	0
Restructuring Reserve, Settled without Cash	0	(190)
2016 Restructuring Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	6	30		6
Adjustment to restructuring reserves	0
Restructuring and impairment costs		62
Payments for Restructuring	(2)	0
Restructuring Reserve, Settled without Cash	0	(32)
2016 Restructuring Plan [Member] | Currency Translation
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	2	1		$ 2
Adjustment to restructuring reserves	0
Restructuring and impairment costs		0
Payments for Restructuring	0	0
Restructuring Reserve, Settled without Cash	1	1
2016 Restructuring Plan [Member] | Adient | Discontinued Operations
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		332
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)
Committed restructuring liabilities assumed from Tyco Merger [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		56
Committed restructuring liabilities assumed from Tyco Merger [Member] | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		78
Restructuring Reserve, Settled without Cash	(22)
Committed restructuring liabilities assumed from Tyco Merger [Member] | Fixed Asset Impairment
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		0
Restructuring Reserve, Settled without Cash	0
Committed restructuring liabilities assumed from Tyco Merger [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		0
Restructuring Reserve, Settled without Cash	0
Committed restructuring liabilities assumed from Tyco Merger [Member] | Currency Translation
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		0
Restructuring Reserve, Settled without Cash	0
Building Solutions Asia Pacific | 2017 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	16
Corporate | 2017 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	166
Corporate | 2016 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		161
Power Solutions | 2017 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	20
Power Solutions | 2016 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		66
Building Solutions EMEA/LA | 2017 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	74
Building Solutions EMEA/LA | 2016 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		17
Building Solutions North America | 2017 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	59
Global Products | 2017 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 32
Global Products | 2016 Restructuring Plan [Member] | Continuing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs		$ 44