Acquisition, Dispositions, Goodwill and Other Intangible Assets (Goodwill) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Line Items]
Goodwill - Beginning Balance	$ 27,910
Goodwill Resulting from Business Combinations	57
Goodwill - Foreign Currency Translation and Other	372
Goodwill - Ending Balance	28,339
Otis [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	1,737
Goodwill Resulting from Business Combinations	0
Goodwill - Foreign Currency Translation and Other	39
Goodwill - Ending Balance	1,776
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	229
Goodwill - Ending Balance	10,239
Pratt & Whitney [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	1,511
Goodwill Resulting from Business Combinations	56
Goodwill - Foreign Currency Translation and Other	(2)
Goodwill - Ending Balance	1,565
UTC Aerospace Systems [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	14,650
Goodwill Resulting from Business Combinations	0
Goodwill - Foreign Currency Translation and Other	106
Goodwill - Ending Balance	14,756
Total Segments [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	27,907
Goodwill Resulting from Business Combinations	57
Goodwill - Foreign Currency Translation and Other	372
Goodwill - Ending Balance	28,336
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