Restructuring and Other Costs (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 69
Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	39
Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	30
Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	12
Restructuring Reserve	8
Net pre-tax restructuring costs (reversals)	12
Utilization and foreign exchange	4
Expected Costs	52
Remaining Costs	40
Current Year Actions [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	4
Current Year Actions [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	8
Current Year Actions [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	8
Net pre-tax restructuring costs (reversals)	11
Utilization and foreign exchange	3
Current Year Actions [Member] | Facility Exit, Lease Termination and Other Costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	0
Net pre-tax restructuring costs (reversals)	1
Utilization and foreign exchange	1
Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	51
Restructuring Reserve	86	$ 85
Net pre-tax restructuring costs (reversals)	51	176
Utilization and foreign exchange	50
Expected Costs	330
Remaining Costs	103
Prior Year Actions [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	30
Prior Year Actions [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	21
Prior Year Actions [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	88	84
Net pre-tax restructuring costs (reversals)	39
Utilization and foreign exchange	35
Prior Year Actions [Member] | Facility Exit, Lease Termination and Other Costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	(2)	1
Net pre-tax restructuring costs (reversals)	12
Utilization and foreign exchange	15
Two Years Prior Actions [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	6
Restructuring Reserve	108
Otis [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	26
Otis [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	9
Expected Costs	13
Remaining Costs	4
Otis [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	15	43
Expected Costs	74
Remaining Costs	16
UTC Climate, Controls & Security [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	14
UTC Climate, Controls & Security [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	1
Expected Costs	22
Remaining Costs	21
UTC Climate, Controls & Security [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	7	76
Expected Costs	90
Remaining Costs	7
Pratt & Whitney [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0
Pratt & Whitney [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	0
Expected Costs	0
Remaining Costs	0
Pratt & Whitney [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	0	7
Expected Costs	7
Remaining Costs	0
UTC Aerospace Systems [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	27
UTC Aerospace Systems [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	0
Expected Costs	15
Remaining Costs	15
UTC Aerospace Systems [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	29	43
Expected Costs	152
Remaining Costs	80
Eliminations and other [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	2
Eliminations and other [Member] | Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	(2)
Expected Costs	2
Remaining Costs	0
Eliminations and other [Member] | Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs (reversals)	0	$ 7
Expected Costs	7
Remaining Costs	$ 0