Acquisition, Dispositions, Goodwill and Other Intangible Assets (Goodwill) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($)
Goodwill [Line Items]
Goodwill - Beginning Balance	$ 27,910
Goodwill Resulting from Business Combinations	85
Goodwill - Foreign Currency Translation and Other	(316)
Goodwill - Ending Balance	27,679
Taylor Company [Member]
Goodwill [Line Items]
Goodwill - Foreign Currency Translation and Other	151
Otis [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	1,737
Goodwill Resulting from Business Combinations	6
Goodwill - Foreign Currency Translation and Other	(42)
Goodwill - Ending Balance	1,701
UTC Climate, Controls & Security [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	10,009
Goodwill Resulting from Business Combinations	1
Goodwill - Foreign Currency Translation and Other	(237)
Goodwill - Ending Balance	9,773
Pratt & Whitney [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	1,511
Goodwill Resulting from Business Combinations	58
Goodwill - Foreign Currency Translation and Other	(2)
Goodwill - Ending Balance	1,567
UTC Aerospace Systems [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	14,650
Goodwill Resulting from Business Combinations	0
Goodwill - Foreign Currency Translation and Other	(35)
Goodwill - Ending Balance	14,615
Total Segments [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	27,907
Goodwill Resulting from Business Combinations	65
Goodwill - Foreign Currency Translation and Other	(316)
Goodwill - Ending Balance	27,656
Eliminations and other [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	3
Goodwill Resulting from Business Combinations	20
Goodwill - Foreign Currency Translation and Other	0
Goodwill - Ending Balance	$ 23