Acquisition, Dispositions, Goodwill and Other Intangible Assets (Goodwill) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Goodwill [Line Items]
Goodwill - Beginning Balance	$ 27,910
Goodwill Resulting from Business Combinations	63
Goodwill - Foreign Currency Translation and Other	(274)
Goodwill - Ending Balance	27,699
Taylor Company [Member]
Goodwill [Line Items]
Goodwill - Foreign Currency Translation and Other	150
Otis [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	1,737
Goodwill Resulting from Business Combinations	5
Goodwill - Foreign Currency Translation and Other	(34)
Goodwill - Ending Balance	1,708
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	(211)
Goodwill - Ending Balance	9,799
Pratt & Whitney [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	1,511
Goodwill Resulting from Business Combinations	57
Goodwill - Foreign Currency Translation and Other	(3)
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	(26)
Goodwill - Ending Balance	14,624
Total Segments [Member]
Goodwill [Line Items]
Goodwill - Beginning Balance	27,907
Goodwill Resulting from Business Combinations	63
Goodwill - Foreign Currency Translation and Other	(274)
Goodwill - Ending Balance	27,696
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