Revenue Recognition (Details) - USD ($)	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Oct. 01, 2018
Disaggregation of Revenue [Line Items]
Contract with Customer Asset Liability Net	$ (95,000,000)		$ (102,000,000)
Revenue, Net	5,464,000,000	$ 5,305,000,000
Contract with Customer, Liability, Revenue Recognized	712,000,000
Revenue, Remaining Performance Obligation	$ 13,700,000,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Explanation	60.00%
Capitalized Contract Cost, Gross	$ 175,000,000
Capitalized Contract Cost, Amortization	35,000,000
Capitalized Contract Cost, Impairment Loss	0
Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	3,922,000,000
Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,542,000,000
Building Solutions North America
Disaggregation of Revenue [Line Items]
Revenue, Net	2,116,000,000
Building Solutions North America | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,321,000,000
Building Solutions North America | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	795,000,000
Building Solutions EMEA/LA
Disaggregation of Revenue [Line Items]
Revenue, Net	907,000,000
Building Solutions EMEA/LA | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	417,000,000
Building Solutions EMEA/LA | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	490,000,000
Building Solutions Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue, Net	613,000,000
Building Solutions Asia Pacific | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	356,000,000
Building Solutions Asia Pacific | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	257,000,000
Global Products
Disaggregation of Revenue [Line Items]
Revenue, Net	1,828,000,000
Global Products | Global Products- Building Management [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	281,000,000
Global Products | Global Products- HVAC & Refrigeration Equipment [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,285,000,000
Global Products | Global Products- Specialty [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	262,000,000
Global Products | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,828,000,000
Global Products | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	0
Other Current Assets
Disaggregation of Revenue [Line Items]
Capitalized Contract Cost, Gross	91,000,000
Accounts Receivable [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Gross, Current	1,320,000,000
Contract with Customer, Asset, Net, Current			1,261,000,000
Other Noncurrent Assets
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Gross, Noncurrent	73,000,000		85,000,000
Capitalized Contract Cost, Gross	84,000,000
Deferred Revenue [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability, Current	(1,378,000,000)		(1,335,000,000)
Other Noncurrent Liabilities [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability, Noncurrent	$ (110,000,000)		$ (113,000,000)