Revenue Recognition (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Oct. 01, 2018	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Contract with Customer Asset Liability Net	$ (212,000,000)		$ (212,000,000)		$ (102,000,000)
Revenue, Net	5,779,000,000	$ 5,630,000,000	11,243,000,000	$ 10,935,000,000
Contract with Customer, Liability, Revenue Recognized	214,000,000		926,000,000
Deferred revenue	(1,521,000,000)		(1,521,000,000)			$ (1,326,000,000)
Revenue, Remaining Performance Obligation, Amount	$ 13,900,000,000		$ 13,900,000,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Explanation	60.00%		60.00%
Capitalized Contract Cost, Gross	$ 184,000,000		$ 184,000,000
Capitalized Contract Cost, Amortization	34,000,000		69,000,000
Capitalized Contract Cost, Impairment Loss			0
Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	4,240,000,000		8,162,000,000
Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,539,000,000		3,081,000,000
Building Solutions North America
Disaggregation of Revenue [Line Items]
Revenue, Net	2,187,000,000		4,303,000,000
Building Solutions North America | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,387,000,000		2,708,000,000
Building Solutions North America | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	800,000,000		1,595,000,000
Building Solutions EMEA/LA
Disaggregation of Revenue [Line Items]
Revenue, Net	878,000,000		1,785,000,000
Building Solutions EMEA/LA | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	416,000,000		833,000,000
Building Solutions EMEA/LA | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	462,000,000		952,000,000
Building Solutions Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue, Net	628,000,000		1,241,000,000
Building Solutions Asia Pacific | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	351,000,000		707,000,000
Building Solutions Asia Pacific | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	277,000,000		534,000,000
Global Products
Disaggregation of Revenue [Line Items]
Revenue, Net	2,086,000,000		3,914,000,000
Global Products | Global Products- Building Management [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	320,000,000		601,000,000
Global Products | Global Products- HVAC & Refrigeration Equipment [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	1,474,000,000		2,759,000,000
Global Products | Global Products- Specialty [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	292,000,000		554,000,000
Global Products | Products and Systems [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	2,086,000,000		3,914,000,000
Global Products | Services [Domain]
Disaggregation of Revenue [Line Items]
Revenue, Net	0		0
Other Current Assets
Disaggregation of Revenue [Line Items]
Capitalized Contract Cost, Gross	98,000,000		98,000,000
Accounts Receivable [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Gross, Current	1,343,000,000		1,343,000,000
Contract with Customer, Asset, Net, Current					1,261,000,000
Other Noncurrent Assets
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Gross, Noncurrent	85,000,000		85,000,000		85,000,000
Capitalized Contract Cost, Gross	86,000,000		86,000,000
Deferred Revenue [Member]
Disaggregation of Revenue [Line Items]
Deferred revenue	(1,521,000,000)		(1,521,000,000)		(1,335,000,000)
Other Noncurrent Liabilities [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability, Noncurrent	$ (119,000,000)		$ (119,000,000)		$ (113,000,000)