Discontinued Operations Discontinued Operations Additional Information (Details)	3 Months Ended						12 Months Ended
	Sep. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations attributable to noncontrolling interests							$ 9,000,000	$ 84,000,000	$ 70,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent							(43,000,000)	(1,600,000,000)	749,000,000
Restructuring Charges							367,000,000	288,000,000	215,000,000
Net actuarial (gain) loss							$ 420,000,000	(393,000,000)	(416,000,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent							35.00%
Income Tax Expense (Benefit)							$ 705,000,000	197,000,000	71,000,000
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ 53,000,000						34,000,000	(29,000,000)	(7,000,000)
Deferred income taxes							563,000,000	(765,000,000)	242,000,000
Adient
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales, Discontinued Operations							1,434,000,000	16,837,000,000	20,079,000,000
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax							1,000,000	525,000,000	1,220,000,000
Provision for income taxes on discontinued operations							35,000,000	2,041,000,000	529,000,000
Income from discontinued operations attributable to noncontrolling interests							9,000,000	84,000,000	66,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent							(43,000,000)	(1,600,000,000)	625,000,000
Separation costs							79,000,000	418,000,000
Restructuring Charges								332,000,000	182,000,000
Net actuarial (gain) loss								110,000,000	6,000,000
Gain (Loss) from Disposal of Discontinued Operation, before Income Tax									155,000,000
Transaction and separation costs									52,000,000
Income Tax Expense (Benefit)								95,000,000
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount		$ 85,000,000
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount			$ 780,000,000
Deferred income taxes								24,000,000
Global Workplace Solutions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net Sales, Discontinued Operations									3,025,000,000
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax									1,203,000,000
Provision for income taxes on discontinued operations									1,075,000,000
Income from discontinued operations attributable to noncontrolling interests									4,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent							$ 0		124,000,000
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount									680,000,000
Transaction costs, divestiture related									87,000,000
Automotive Experience Interiors | Yanfeng Automotive Trim Systems [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax				$ 145,000,000
Gain (Loss) from Disposal of Discontinued Operation, before Income Tax				145,000,000
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax				38,000,000
Automotive Experience Interiors | Interiors
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount				223,000,000	$ 75,000,000
Global Workplace Solutions | Brookfield Johnson Controls [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax						$ 200,000,000
Gain (Loss) from Disposal of Discontinued Operation, before Income Tax									200,000,000
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax						$ 127,000,000
Discontinued Operation, Tax Effect of Gain from Disposal of Discontinued Operation									73,000,000
Number of Joint Ventures Divested						2
Global Workplace Solutions | CBRE Group, Inc. [Member] [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax				940,000,000
Gain (Loss) from Disposal of Discontinued Operation, before Income Tax									940,000,000
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax				$ 643,000,000
Ongoing Strategic Relationship With Buyer in Divestiture of Business						10 years
Discontinued Operation, Tax Effect of Gain from Disposal of Discontinued Operation									$ 297,000,000
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								$ 1,891,000,000