Acquisitions, Dispositions, Goodwill and Intangible Assets (General Information) (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Jan. 08, 2021	Apr. 03, 2020	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill			$ 54,265		$ 54,285
Proceeds from Divestiture of Businesses and Interests in Affiliates			1,049	$ 0
Assets			160,608		162,153
Liabilities			87,266		88,269
Forcepoint
Business Acquisition [Line Items]
Proceeds from Divestiture of Businesses and Interests in Affiliates	$ 1,000
Forcepoint | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Business Acquisition [Line Items]
Assets					1,900
Liabilities					855
Goodwill and intangible assets					$ 1,400
Carrier [Member]
Business Acquisition [Line Items]
Shares of common stock distributed in the Distribution		866,158,910
Otis [Member]
Business Acquisition [Line Items]
Shares of common stock distributed in the Distribution		433,079,455
Raytheon Company [Member]
Business Acquisition [Line Items]
Business Acquisition UTC stock payable shares		2.3348
Fair value of RTC common stock issued for Raytheon Company outstanding common stock and vested equity awards		$ 33,067
Fair value attributable to pre-merger service for replacement equity awards		99
Total estimated merger consideration		$ 33,166
Common Stock, Shares, Outstanding		277,300,000
Stock awards vested as a result of the Raytheon Merger		400,000
Total outstanding shares entitled to merger consideration		277,700,000
Shares of RTC common stock issued for Raytheon Company outstanding common stock and vested equity awards		648,400,000
Price per share of RTC common stock		$ 51.00
Goodwill, Purchase Accounting Adjustments			61
Cash and cash equivalents		$ 3,208
Accounts receivable		1,997
Inventory		705
Contract assets		6,023
Other assets, current		940
Fixed assets		4,745
Operating lease right-of-use assets		950
Intangible assets:		19,130
Other assets		1,218
Total identifiable assets acquired		38,916
Accounts payable		1,477
Accrued employee compensation		1,492
Other accrued liabilities		1,921
Contract liabilities		3,002
Long-term debt, including current portion		4,700
Operating lease liabilities, non-current portion		738
Future pension and postretirement benefit obligation		11,607
Other long-term liabilities		2,368
Total liabilities acquired		27,305
Total identifiable net assets		11,611
Goodwill		21,589
Redeemable noncontrolling interest		(34)
Total consideration transferred		33,166
Fair value adjustments to fixed assets		1,100
Fair value adjustment to future pension and postretirement benefit obligations		3,600
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Loss Contracts		222
Business Combination, Acquisition Related Costs			$ 17	29
Net sales				18,451
Income from continuing operations attributable to common shareowners				$ 1,239
Basic earnings per share of common stock from continuing operations				$ 0.82
Diluted earnings per share of common stock from continuing operations				$ 0.82
Amortization of acquired Raytheon Company intangible assets, net (1)				$ (270)
Amortization of fixed asset fair value adjustment (2)				(9)
Utilization of contractual customer obligation (3)				8
Deferred revenue fair value adjustment (4)				(4)
Adjustment to non-service pension (income) expense (5)				239
RTC/Raytheon fees for advisory, legal, accounting services (6)				35
Adjustment to interest expense related to the Raytheon Merger, net (7)				9
Elimination of deferred commission amortization (8)				5
Pro Forma Nonrecurring Adjustments, Net				$ 13
Raytheon Company [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Finite-Lived Intangibles		$ 12,900
Finite-Lived Intangible Asset, Useful Life		25 years
Raytheon Company [Member] | Trademarks
Business Acquisition [Line Items]
Finite-Lived Intangibles		$ 5,430
Raytheon Company [Member] | Developed technology and other
Business Acquisition [Line Items]
Finite-Lived Intangibles		$ 800
Raytheon Company [Member] | Developed technology and other | Maximum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		7 years
Raytheon Company [Member] | Developed technology and other | Minimum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years