Restructuring Costs (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	$ 19			$ 118
Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	4			25
Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	15			93
Pratt & Whitney [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	2			6
Collins Aerospace Systems [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	2			32
Eliminations and other [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	15			80
Current Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	12			113
Utilization, foreign exchange and other costs				(37)
Restructuring Reserve	76			76	$ 0
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	187			187
Costs Incurred	(12)	$ (65)	$ (36)
Remaining Costs	74			74
Current Year Actions [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	7			32
Current Year Actions [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	5			81
Current Year Actions [Member] | Pratt & Whitney [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	58			58
Costs Incurred	(1)	(2)	(20)
Remaining Costs	35			35
Current Year Actions [Member] | Collins Aerospace Systems [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	67			67
Costs Incurred	(9)	(3)	(16)
Remaining Costs	39			39
Current Year Actions [Member] | Eliminations and other [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	62			62
Costs Incurred	(2)	(60)	0
Remaining Costs	0			0
Prior Year Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	1			(19)
Utilization, foreign exchange and other costs				(245)
Restructuring Reserve	76			76	340
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	758			758
Costs Incurred	(1)	24	(4)		(770)
Remaining Costs	7			7
Prior Year Actions [Member] | Cost of Sales [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	(6)			(14)
Prior Year Actions [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	7			(5)
Prior Year Actions [Member] | Pratt & Whitney [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	188			188
Costs Incurred	0	17	0		(205)
Remaining Costs	0			0
Prior Year Actions [Member] | Collins Aerospace Systems [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	320			320
Costs Incurred	12	7	1		(333)
Remaining Costs	7			7
Prior Year Actions [Member] | Eliminations and other [Member]
Restructuring and Related Cost, Expected Cost [Abstract]
Expected Costs	250			250
Costs Incurred	(13)	$ 0	$ (5)		$ (232)
Remaining Costs	0			0
Two Years Prior Actions [Member]
Restructuring Cost and Reserve [Line Items]
Net pre-tax restructuring costs	6			24
Restructuring Reserve	$ 28			$ 28