Discontinued Operations Discontinued Operations, Income Statement Disclosures - Adient Spinoff (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Sep. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations attributable to noncontrolling interests				$ 0	$ 9	$ 84
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent				0	(43)	(1,600)
Restructuring and impairment costs				263	367	288
Net actuarial (gain) loss				10	$ 420	(393)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					12.50%
Income Tax Expense (Benefit)				518	$ 705	197
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ 53			31	(164)	(29)
Deferred income taxes				$ (636)	563	(765)
Adient
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales, Discontinued Operations					1,434	16,837
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax					1	525
Provision for income taxes on discontinued operations					35	2,041
Income from discontinued operations attributable to noncontrolling interests					9	84
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent					(43)	(1,600)
Separation costs					79	418
Restructuring and impairment costs						332
Net actuarial (gain) loss						110
Income Tax Expense (Benefit)						95
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount		$ 85
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount			$ 780
Deferred income taxes						24
Substantial business reorganizations [Member] | Adient
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount						1,891
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member] | Adient
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred income taxes					$ 562	$ (476)