Revenue Recognition Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue, Net	$ 5,343	$ 6,451	$ 16,363	$ 17,694
Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	3,919	4,896	11,877	13,058
Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,424	1,555	4,486	4,636
Building Solutions North America
Disaggregation of Revenue [Line Items]
Revenue, Net	2,020	2,327	6,362	6,630
Building Solutions North America | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,250	1,494	3,963	4,202
Building Solutions North America | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	770	833	2,399	2,428
Building Solutions EMEA/LA
Disaggregation of Revenue [Line Items]
Revenue, Net	756	922	2,534	2,707
Building Solutions EMEA/LA | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	346	464	1,203	1,297
Building Solutions EMEA/LA | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	410	458	1,331	1,410
Building Solutions Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue, Net	588	691	1,742	1,932
Building Solutions Asia Pacific | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	344	427	986	1,134
Building Solutions Asia Pacific | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	244	264	756	798
Global Products
Disaggregation of Revenue [Line Items]
Revenue, Net	1,979	2,511	5,725	6,425
Global Products | Global Products- Building Management Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	244	342	860	943
Global Products | Global Products- HVAC & Refrigeration Equipment [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,493	1,869	4,085	4,628
Global Products | Global Products- Specialty Products [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	242	300	780	854
Global Products | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,979	2,511	5,725	6,425
Global Products | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	$ 0	$ 0	$ 0	$ 0