Segment Information Financial Information Related to Company's Reportable Segments (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2021	Sep. 30, 2020		Sep. 30, 2019
Segment Information [Line Items]
Net sales		$ 23,668	$ 22,317		$ 23,968
Segment EBITA		3,385	2,948		3,041
Amortization of Intangible Assets		(435)	(386)		(377)
General corporate expenses	[1]	(290)	(371)		(405)
Net financing charges		(206)	(231)		(350)
Restructuring and impairment costs		(242)	(783)		(235)
Mark-to-market gain (loss)		402	(274)		(618)
Income from continuing operations before income taxes		2,614	903		1,056
Assets		41,890	40,815		42,287
Assets held for sale		156	147		158
Depreciation and amortization		845	822		825
Capital expenditures		552	443		586
Equity income in segment income		261	171		192
Building Solutions North America
Segment Information [Line Items]
Net sales		8,685	8,605
Equity Method Investments		8	7		8
Building Solutions EMEA/LA
Segment Information [Line Items]
Net sales		3,727	3,440
Equity Method Investments		111	108		109
Building Solutions Asia Pacific
Segment Information [Line Items]
Net sales		2,654	2,403
Equity Method Investments		2	2		6
Global Products
Segment Information [Line Items]
Net sales		8,602	7,869
Equity Method Investments		945	797		730
Building Technologies & Solutions
Segment Information [Line Items]
Assets		38,669	36,806		36,950
Depreciation and amortization		805	773		764
Capital expenditures		511	419		548
Building Technologies & Solutions | Building Solutions North America
Segment Information [Line Items]
Net sales		8,685	8,605		9,031
Segment EBITA	[2]	1,204	1,157		1,153
Restructuring and impairment costs		(70)	(520)
Assets	[3]	15,317	15,215		15,562
Depreciation and amortization		245	233		233
Capital expenditures		87	93		119
Equity income in segment income		5	(1)
Building Technologies & Solutions | Building Solutions EMEA/LA
Segment Information [Line Items]
Net sales		3,727	3,440		3,655
Segment EBITA	[4]	391	338		368
Restructuring and impairment costs		(29)	(59)
Assets	[5]	5,241	4,989		4,786
Depreciation and amortization		103	102		112
Capital expenditures		128	99		93
Equity income in segment income		5	6		12
Building Technologies & Solutions | Building Solutions Asia Pacific
Segment Information [Line Items]
Net sales		2,654	2,403		2,658
Segment EBITA	[6]	349	319		341
Restructuring and impairment costs		(28)	(56)
Assets	[7]	2,783	2,720		2,657
Depreciation and amortization		25	24		23
Capital expenditures		31	36		26
Equity income in segment income		1	1		1
Building Technologies & Solutions | Global Products
Segment Information [Line Items]
Net sales		8,602	7,869		8,624
Segment EBITA	[8]	1,441	1,134		1,179
Restructuring and impairment costs		(91)	(143)		(235)
Assets		15,328	13,882	[9]	13,945	[9]
Depreciation and amortization		432	414		396
Capital expenditures		265	191		310
Equity income in segment income		250	166		179
Unallocated
Segment Information [Line Items]
Assets		3,065	3,862		5,179
Corporate
Segment Information [Line Items]
Restructuring and impairment costs		(24)	(5)
Depreciation and amortization		40	49		61
Capital expenditures		41	24		38
Continuing Operations [Member]
Segment Information [Line Items]
Depreciation and amortization		845	822		825
Capital expenditures		552	443		586
Discontinued Operations
Segment Information [Line Items]
Depreciation and amortization		0	0		32
Capital expenditures		0	0		197
Continuing and Discontinued Operations [Member]
Segment Information [Line Items]
Depreciation and amortization		845	822		857
Capital expenditures		$ 552	$ 443		$ 783

[1] Corporate expenses for the year ended September 30, 2021 and 2020 excludes $24 million and $5 million, respectively, of restructuring and impairment costs.

[2] Building Solutions North America segment EBITA for the year ended September 30, 2021 and 2020 excludes $70 million and $520 million, respectively, of restructuring and impairment costs. For the year ended September 30, 2021, Building Solutions North America includes $5 million of equity income. For the year ended September 30, 2020, Building Solutions North America includes $1 million of equity losses.

[3] Buildings Solutions North America assets as of September 30, 2021, 2020 and 2019 include $8 million, $7 million and $8 million, respectively, of investments in partially-owned affiliates.

[4] Building Solutions EMEA/LA segment EBITA for the years ended September 30, 2021 and 2020 excludes $29 million and $59 million, respectively, of restructuring and impairment costs. For the years ended September 30, 2021, 2020 and 2019, Building Solutions EMEA/LA segment EBITA includes $5 million, $6 million and $12 million, respectively, of equity income.

[5] Building Solutions EMEA/LA assets as of September 30, 2021, 2020 and 2019 include $111 million, $108 million and $109 million, respectively, of investments in partially-owned affiliates.

[6] Building Solutions Asia Pacific segment EBITA for the year ended September 30, 2021 and 2020 excludes $28 million and $56 million, respectively, of restructuring and impairment costs. For the years ended September 30, 2021, 2020 and 2019, Building Solutions Asia Pacific segment EBITA includes $1 million, less than $1 million and less than $1 million, respectively, of equity income.

[7] Building Solutions Asia Pacific assets as of September 30, 2021, 2020 and 2019 include $2 million, $2 million, and $6 million, respectively, of investments in partially-owned affiliates.

[8] Global Products segment EBITA for the years ended September 30, 2021, 2020 and 2019 excludes $91 million, $143 million and $235 million, respectively, of restructuring and impairment costs. For the years ended September 30, 2021, 2020 and 2019, Global Products segment EBITA includes $250 million, $166 million and $179 million, respectively, of equity income.

[9] Global Products assets as of September 30, 2021, 2020 and 2019 include $945 million, $797 million and $730 million, respectively, of investments in partially-owned affiliates.