Acquisition, Dispositions, Goodwill and Other Intangible Assets (Goodwill) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Goodwill [Line Items]
Goodwill - Beginning Balance	$ 27,059
Goodwill Resulting from Business Combinations	113
Goodwill - Foreign Currency Translation and Other	744
Goodwill - Ending Balance	27,916
Otis [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	1,575
Goodwill Resulting from Business Combinations	3
Goodwill - Foreign Currency Translation and Other	114
Goodwill - Ending Balance	1,692
UTC Climate, Controls & Security [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	9,487
Goodwill Resulting from Business Combinations	110
Goodwill - Foreign Currency Translation and Other	443
Goodwill - Ending Balance	10,040
Pratt & Whitney [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	1,511
Goodwill Resulting from Business Combinations	0
Goodwill - Foreign Currency Translation and Other	0
Goodwill - Ending Balance	1,511
UTC Aerospace Systems [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	14,483
Goodwill Resulting from Business Combinations	0
Goodwill - Foreign Currency Translation and Other	187
Goodwill - Ending Balance	14,670
Total Segments [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	27,056
Goodwill Resulting from Business Combinations	113
Goodwill - Foreign Currency Translation and Other	744
Goodwill - Ending Balance	27,913
Eliminations and other [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	3
Goodwill Resulting from Business Combinations	0
Goodwill - Foreign Currency Translation and Other	0
Goodwill - Ending Balance	$ 3