Income Taxes Other Tax Matters (Details) - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Other Tax Matters [Line Items]
Nondeductible expense related to restructuring and impairment						$ 65	$ 28	$ 0
Income tax provision						705	197	71
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ 53					34	(29)	(7)
Restructuring and impairment costs						367	288	215
Post sale contingent tax indemnification liabilities	290		$ 290			290	290
Tax indemnification liabilities related to other divestitures	11					11
Scott Safety business [Member]
Other Tax Matters [Line Items]
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount						490
Business Divestitures, Not Specific
Other Tax Matters [Line Items]
Post sale contingent tax indemnification liabilities	255					255
(Loss) on divestiture	$ (9)		(12)					(10)
Global Workplace Solutions
Other Tax Matters [Line Items]
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount								680
Discontinued Operation, Income from Discontinued Operation, before Income Tax								$ (1,203)
Automotive Experience Interiors | Yanfeng Automotive Trim Systems [Member]
Other Tax Matters [Line Items]
Discontinued Operation, Income from Discontinued Operation, before Income Tax				$ (145)
Discontinued Operation, Gain on Disposal of Discontinued Operation, Net of Tax				38
Automotive Experience Interiors | Interiors
Other Tax Matters [Line Items]
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount				$ 223	$ 75
2016 Restructuring Plan [Member]
Other Tax Matters [Line Items]
Restructuring and impairment costs							$ 620
Transaction and integration costs [Member]
Other Tax Matters [Line Items]
Transaction and integration costs						428
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount						$ 69
Tyco Merger [Member]
Other Tax Matters [Line Items]
Income tax provision			$ 137
Adient spin-off [Member]
Other Tax Matters [Line Items]
Income tax provision		$ 26
Change in Entity Status [Domain]
Other Tax Matters [Line Items]
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount		$ 101