Acquisitions, Dispositions, Goodwill and Other Intangible Assets (General Information) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Apr. 03, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill Resulting from Business Combinations				$ 19,983
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
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	3,208
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	1,997
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory	705
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contract Assets	6,023
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	897
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets	14
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	4,732
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	19,130
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	2,139
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	38,845
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	1,455
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accrued Liabilities	3,235
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Contract Liabilities	2,991
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	4,700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Pension and Postretirement Liabilities	10,651
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	3,482
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	26,514
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	12,331
Goodwill	20,869	$ 53,269		53,269		$ 36,609
Business Combination, Acquisition of Noncontrolling Interest, Fair Value	(34)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	33,166
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Loss Contracts	$ 218
Proceeds from Divestiture of Businesses and Interests in Affiliates				234	$ 133
Gain on disposal recorded as an adjustment to fair value of net asset acquired				210
Assets		161,517		161,517		139,615
Liabilities		92,590		92,590		$ 95,289
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Business Acquisition [Line Items]
Assets		1,814		1,814
Liabilities		90		90
Goodwill and intangible assets		1,600		$ 1,600
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
Customer Relationships [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 12,900
Finite-Lived Intangible Asset, Useful Life	25 years
Customer Relationships [Member] | Maximum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life				32 years
Customer Relationships [Member] | Minimum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life				1 year
Trademarks
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 5,430
Developed Technology Rights
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 800
Developed Technology Rights | Maximum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life				25 years
Developed Technology Rights | Minimum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life				5 years
Raytheon Company [Member]
Business Acquisition [Line Items]
Business Acquisition UTC stock payable shares	2.3348
Pro Forma Nonrecurring Adjustment, Amortization of acquired Rockwell Collins intangible assets, net		0	$ (262)	$ (270)	(525)
Pro Forma Nonrecurring Adjustment, Amortization of inventory and fixed asset fair value adjustment		0	(9)	(9)	(18)
Pro Forma Nonrecurring Adjustment, Utilization of contractual customer obligation		0	15	8	29
Pro Forma Nonrecurring Adjustment, Adjustment to net periodic pension cost		0	208	239	416
Pro Forma Nonrecurring Adjustment, Deferred revenue fair value adjustment		0	(8)	(4)	(17)
Pro Forma Nonrecurring Adjustment, RTC/Raytheon fees for advisory, legal, accounting services		61	45	96	(96)
Pro Forma Nonrecurring Adjustment, Interest expense related to debt distributions and Raytheon Merger, net		0	9	9	18
Pro Forma Nonrecurring Adjustment, Elimination of deferred commission amortization		0	7	5	10
Pro Forma Nonrecurring Adjustments, Net		61	5	74	(183)
Business Acquisition, Pro Forma Net Income (Loss)		(3,732)	2,006	(3,014)	3,308
Business Acquisition, Pro Forma Revenue		$ 14,470	$ 18,416	$ 32,921	$ 36,038
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Basic		$ (2.49)	$ 1.33	$ (2.08)	$ 2.20
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Diluted		$ (2.49)	$ 1.32	$ (2.07)	$ 2.19
Business Combination, Acquisition Related Costs		$ 70		$ 99
Goodwill Resulting from Business Combinations		$ 20,900
Fair value of RTC common stock issued for Raytheon Company outstanding common stock and vested equity awards	$ 33,067
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
Fair value adjustments to fixed assets	$ 1,100
Fair value adjustment to future pension and postretirement benefit obligations	$ 2,600
Raytheon Company [Member] | Developed Technology Rights | Maximum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years
Raytheon Company [Member] | Developed Technology Rights | Minimum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years