Restructuring Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	$ 43
Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	20
Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	23
Pratt & Whitney [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	20
Collins Aerospace Systems [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	18
Eliminations and other [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	5
Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	36
Utilization, foreign exchange and other costs	(4)
Restructuring Reserve	32		$ 0
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	69
Costs Incurred		$ (36)
Remaining Costs	33
Current Year Actions [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	24
Utilization, foreign exchange and other costs	(1)
Restructuring Reserve	23		0
Current Year Actions [Member] | Facility Exit, Lease Termination and Other Costs
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	12
Utilization, foreign exchange and other costs	(3)
Restructuring Reserve	9		0
Current Year Actions [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	21
Current Year Actions [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	15
Current Year Actions [Member] | Pratt & Whitney [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	20
Costs Incurred		(20)
Remaining Costs	0
Current Year Actions [Member] | Collins Aerospace Systems [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	49
Costs Incurred		(16)
Remaining Costs	33
Current Year Actions [Member] | Eliminations and other [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	0
Costs Incurred		$ 0
Remaining Costs	0
Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	4
Utilization, foreign exchange and other costs	(135)
Restructuring Reserve	209		340
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	782
Costs Incurred	(4)		(770)
Remaining Costs	8
Prior Year Actions [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	1
Utilization, foreign exchange and other costs	(130)
Restructuring Reserve	205		334
Prior Year Actions [Member] | Facility Exit, Lease Termination and Other Costs
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	3
Utilization, foreign exchange and other costs	(5)
Restructuring Reserve	4		6
Prior Year Actions [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	(2)
Prior Year Actions [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	6
Prior Year Actions [Member] | Pratt & Whitney [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	205
Costs Incurred	0		(205)
Remaining Costs	0
Prior Year Actions [Member] | Collins Aerospace Systems [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	340
Costs Incurred	1		(333)
Remaining Costs	8
Prior Year Actions [Member] | Eliminations and other [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	237
Costs Incurred	(5)		$ (232)
Remaining Costs	0
Two Years Prior Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	3
Restructuring Reserve	$ 32