Restructuring and Other Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			$ (149)
Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(86)
Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(65)
Non-service pension cost (benefit) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(2)
Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(73)
Restructuring Reserve	$ 48	$ 8	48
Net pre-tax restructuring costs (reversals)	61	12	73
Utilization and foreign exchange	21		25
Expected Costs	135		135
Remaining Costs	62		62
Current Year Actions [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(38)
Current Year Actions [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(37)
Current Year Actions [Member] | Non-service pension cost (benefit) [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(2)
Current Year Actions [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	48	8	48
Net pre-tax restructuring costs (reversals)	60		71
Utilization and foreign exchange	20		23
Current Year Actions [Member] | Facility Exit, Lease Termination and Other Costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	0	0	0
Net pre-tax restructuring costs (reversals)	1		2
Utilization and foreign exchange	1		2
Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(67)
Restructuring Reserve	70	86	70	$ 85
Net pre-tax restructuring costs (reversals)	16	51	67	176
Utilization and foreign exchange	32		82
Expected Costs	325		325
Remaining Costs	82		82
Prior Year Actions [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(42)
Prior Year Actions [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(25)
Prior Year Actions [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	73	88	73	84
Net pre-tax restructuring costs (reversals)	8		47
Utilization and foreign exchange	23		58
Prior Year Actions [Member] | Facility Exit, Lease Termination and Other Costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	(3)	(2)	(3)	1
Net pre-tax restructuring costs (reversals)	8		20
Utilization and foreign exchange	9		24
Two Years Prior Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(9)
Restructuring Reserve	91		91
Otis [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(47)
Otis [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	18	9
Expected Costs	31		31
Remaining Costs	4		4
Otis [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	4	15		43
Expected Costs	73		73
Remaining Costs	11		11
UTC Climate, Controls & Security [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(35)
UTC Climate, Controls & Security [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	23	1
Expected Costs	77		77
Remaining Costs	53		53
UTC Climate, Controls & Security [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	(5)	7		76
Expected Costs	81		81
Remaining Costs	3		3
Pratt & Whitney [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(3)
Pratt & Whitney [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	3	0
Expected Costs	3		3
Remaining Costs	0		0
Pratt & Whitney [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	0	0		7
Expected Costs	7		7
Remaining Costs	0		0
UTC Aerospace Systems [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(60)
UTC Aerospace Systems [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	15	0
Expected Costs	20		20
Remaining Costs	5		5
UTC Aerospace Systems [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	17	29		43
Expected Costs	157		157
Remaining Costs	68		68
Eliminations and other [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(4)
Eliminations and other [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	(2)	(2)
Expected Costs	4		4
Remaining Costs	0		0
Eliminations and other [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	0	$ 0		$ 7
Expected Costs	7		7
Remaining Costs	$ 0		$ 0