Revenue Recognition Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue, Net	$ 5,594	$ 5,444	$ 10,935	$ 11,020
Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	4,032	3,922	7,831	7,958
Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,562	1,522	3,104	3,062
Building Solutions North America
Disaggregation of Revenue [Line Items]
Revenue, Net	2,092	2,175	4,126	4,342
Building Solutions North America | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,272	1,357	2,514	2,713
Building Solutions North America | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	820	818	1,612	1,629
Building Solutions EMEA/LA
Disaggregation of Revenue [Line Items]
Revenue, Net	897	850	1,803	1,778
Building Solutions EMEA/LA | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	429	400	855	857
Building Solutions EMEA/LA | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	468	450	948	921
Building Solutions Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue, Net	603	525	1,218	1,154
Building Solutions Asia Pacific | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	329	271	674	642
Building Solutions Asia Pacific | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	274	254	544	512
Global Products
Disaggregation of Revenue [Line Items]
Revenue, Net	2,002	1,894	3,788	3,746
Global Products | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	2,002	1,894	3,788	3,746
Global Products | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	0	0	0	0
Global Products | Global Products - HVAC [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,402	1,324	2,651	2,624
Global Products | Global Products - Fire & Security [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	537	511	1,025	1,003
Global Products | Global Products - Industrial Refrigeration [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	$ 63	$ 59	$ 112	$ 119