Segment Information Financial Information Related to Company's Reportable Segments (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Segment Information [Line Items]
Segment EBITA		$ 4,258	$ 2,754	$ 2,327
Amortization of Intangible Assets		(489)	(116)	(74)
General corporate expenses	[1]	(768)	(607)	(417)
Net Sales		30,172	20,837	17,100
Net financing charges		(496)	(289)	(274)
Restructuring and impairment costs		(367)	(288)	(215)
Equity income in segment income		240	174	80
Net mark-to-market adjustments on pension and postretirement plans		(420)	393	416
Income from continuing operations before income taxes		2,558	1,061	931
Total assets		51,884	63,179	29,590
Assets held for sale		2,109	13,186	10,613
Depreciation and amortization		1,188	953	860
Capital expenditures		1,343	1,249	1,135
Building Technologies & Solutions
Segment Information [Line Items]
Segment EBITA		2,831	1,427	1,086
Net Sales		22,835	14,184	10,510
Total assets		36,706	38,506	9,383
Depreciation and amortization		859	304	181
Capital expenditures		653	346	217
Building Technologies & Solutions | Building Solutions North America
Segment Information [Line Items]
Segment EBITA	[2]	1,039	494	416
Net Sales		8,341	4,687	4,270
Restructuring and impairment costs		59		2
Total assets		15,228	15,554	2,300
Depreciation and amortization		272	49	24
Capital expenditures		107	16	17
Building Technologies & Solutions | Building Solutions EMEA/LA
Segment Information [Line Items]
Segment EBITA	[3]	290	74	45
Net Sales		3,595	1,613	1,549
Restructuring and impairment costs		74	17	9
Equity income in segment income		5	11	14
Total assets	[4]	4,885	4,649	1,022
Depreciation and amortization		140	14	10
Building Technologies & Solutions | Building Solutions EMEA/LA
Segment Information [Line Items]
Capital expenditures		98	19	17
Building Technologies & Solutions | Building Solutions Asia Pacific
Segment Information [Line Items]
Segment EBITA	[5]	323	222	211
Net Sales		2,444	1,736	1,651
Restructuring and impairment costs		16		7
Equity income in segment income		1	1
Total assets		2,575	2,521	978
Depreciation and amortization		37	11	9
Capital expenditures		27	7	8
Building Technologies & Solutions | Global Products
Segment Information [Line Items]
Segment EBITA	[6]	1,179	637	414
Net Sales		8,455	6,148	3,040
Restructuring and impairment costs		32	(44)	(20)
Equity income in segment income		151	114	9
Total assets	[7]	14,018	15,782	5,083
Depreciation and amortization		410	230	138
Capital expenditures		421	304	162
Building Technologies & Solutions | Global Workplace Solutions
Segment Information [Line Items]
Capital expenditures		0	0	13
Automotive Experience
Segment Information [Line Items]
Capital expenditures		63	395	455
Automotive Experience | Seating
Segment Information [Line Items]
Capital expenditures		62	392	356
Automotive Experience | Interiors
Segment Information [Line Items]
Capital expenditures		1	3	99
Power Solutions
Segment Information [Line Items]
Segment EBITA	[8]	1,427	1,327	1,241
Net Sales		7,337	6,653	6,590
Restructuring and impairment costs		20	66	11
Equity income in segment income		83	48	57
Total assets	[9]	7,894	6,793	6,531
Depreciation and amortization		236	238	286
Capital expenditures		481	357	252
Unallocated
Segment Information [Line Items]
Total assets		5,175	4,694	3,063
Corporate
Segment Information [Line Items]
Restructuring and impairment costs		166	161	166
Depreciation and amortization		64	80	60
Capital expenditures		146	151	211
Discontinued Operations
Segment Information [Line Items]
Depreciation and amortization		$ 29	$ 331	$ 333

[1] Corporate expenses for the years ended September 30, 2017, 2016 and 2015 excludes $166 million, $161 million and $166 million, respectively, of restructuring and impairment costs.

[2] Building Solutions North America segment EBITA for the years ended September 30, 2017 and 2015 excludes $59 million and $2 million, respectively, of restructuring and impairment costs.

[3] Building Solutions EMEA/LA segment EBITA for the years ended September 30, 2017, 2016 and 2015 excludes $74 million, $17 million and $9 million, respectively, of restructuring and impairment costs. For the years ended September 30, 2017, 2016 and 2015, EMEA/LA segment EBITA includes $5 million, $11 million and $14 million, respectively, of equity income.

[4] Building Solutions EMEA/LA assets as of September 30 2017, 2016 and 2015, include $107 million, $103 million and $90 million, respectively, of investments in partially-owned affiliates.

[5] Building Solutions Asia Pacific segment EBITA for the years ended September 30, 2017 and 2015 excludes $16 million and $7 million, respectively, of restructuring and impairment costs. For the years ended September 30, 2017 and 2016, Asia Pacific segment EBITA includes $1 million and $1 million, respectively, of equity income.

[6] Global Products segment EBITA for the years ended September 30, 2017, 2016 and 2015 excludes $32 million, $44 million and $20 million, respectively, of restructuring and impairment costs. For the years ended September 30, 2017, 2016 and 2015, Global Products segment EBITA includes $151 million, $114 million and $9 million, respectively, of equity income.

[7] Global Products assets as of September 30 2017, 2016 and 2015, include $637 million, $520 million and $64 million, respectively, of investments in partially-owned affiliates.

[8] Power Solutions segment EBITA for the years ended September 30, 2017, 2016 and 2015 excludes $20 million, $66 million and $11 million, respectively, of restructuring and impairment costs. For the years ended September 30, 2017, 2016 and 2015, Power Solutions segment EBITA includes $83 million, $48 million and $57 million, respectively, of equity income.

[9] Power Solutions assets as of September 30 2017, 2016 and 2015, include $447 million, $367 million and $343 million, respectively, of investments in partially-owned affiliates.