Segment Financial Data (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue, Net	$ 15,242	$ 13,815
Operating profit	$ 1,928	$ 2,144
Operating profit margin	12.60%	15.50%
Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue, Net	$ 15,559	$ 14,065
Operating profit	$ 2,043	$ 2,265
Operating profit margin	13.10%	16.10%
Otis [Member]
Segment Reporting Information [Line Items]
Revenue, Net	$ 3,037	$ 2,804
Operating profit	$ 450	$ 447
Operating profit margin	14.80%	15.90%
UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenue, Net	$ 4,376	$ 3,892
Operating profit	$ 592	$ 931
Operating profit margin	13.50%	23.90%
Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenue, Net	$ 4,329	$ 3,758
Operating profit	$ 413	$ 356
Operating profit margin	9.50%	9.50%
UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenue, Net	$ 3,817	$ 3,611
Operating profit	$ 588	$ 531
Operating profit margin	15.40%	14.70%
Eliminations and other [Member]
Segment Reporting Information [Line Items]
Revenue, Net	$ (317)	$ (250)
Operating profit	(11)	(18)
General corporate expenses [Member]
Segment Reporting Information [Line Items]
Revenue, Net	0	0
Operating profit	(104)	$ (103)
United States [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	8,715
United States [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	845
United States [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	2,095
United States [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	3,121
United States [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	2,654
Europe [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	3,170
Europe [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	1,006
Europe [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	1,384
Europe [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	173
Europe [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	607
Asia Pacific [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	2,059
Asia Pacific [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	922
Asia Pacific [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	685
Asia Pacific [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	368
Asia Pacific [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	84
Other [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	1,615
Other [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	264
Other [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	212
Other [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	667
Other [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	472
Commercial and industrial, non aerospace [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	7,449
Commercial and industrial, non aerospace [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	3,037
Commercial and industrial, non aerospace [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	4,376
Commercial and industrial, non aerospace [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	21
Commercial and industrial, non aerospace [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	15
Commercial Aerospace [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	6,110
Commercial Aerospace [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	0
Commercial Aerospace [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	0
Commercial Aerospace [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	3,199
Commercial Aerospace [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	2,911
Military aerospace [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	2,000
Military aerospace [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	0
Military aerospace [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	0
Military aerospace [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	1,109
Military aerospace [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	891
Product [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	10,541
Product [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	1,219
Product [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	3,597
Product [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	2,537
Product [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	3,188
Service [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenues	5,018
Service [Member] | Otis [Member]
Segment Reporting Information [Line Items]
Revenues	1,818
Service [Member] | UTC Climate, Controls & Security [Member]
Segment Reporting Information [Line Items]
Revenues	779
Service [Member] | Pratt & Whitney [Member]
Segment Reporting Information [Line Items]
Revenues	1,792
Service [Member] | UTC Aerospace Systems [Member]
Segment Reporting Information [Line Items]
Revenues	$ 629