Acquisitions, Dispositions, Goodwill and Other Intangible Assets (General Information) (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Nov. 26, 2018
Business Acquisition [Line Items]
Operating Income (Loss)	$ 2,486,000,000	$ 1,838,000,000	$ 7,115,000,000	$ 6,642,000,000
Acquisition Cost Of Acquired Entities and Interest in Affiliates			39,000,000
Proceeds from Issuance of Debt					$ 11,000,000,000.0
Proceeds from Debt, Net of Issuance Costs					$ 10,900,000,000
Goodwill Resulting from Business Combinations			410,000,000
Contractual Obligation, Due in Next Fiscal Year	36,000,000		36,000,000
Contractual Obligation, Due in Second Year	114,000,000		114,000,000
Contractual Obligation, Due in Third Year	101,000,000		101,000,000
Contractual Obligation, Due in Fourth Year	106,000,000		106,000,000
Contractual Obligation, Due in Fifth Year	$ 91,000,000		91,000,000
Business Combination, Acquisition Related Costs			$ 30,000,000	$ 71,000,000
Raytheon Company [Member]
Business Acquisition [Line Items]
Business Acquisition, Date of Acquisition Agreement	Jun. 09, 2019
Business Acquisition, Name of Acquired Entity	Raytheon Company
Business Acquisition UTC stock payable shares	2.3348		2.3348
Rockwell Collins [Member]
Business Acquisition [Line Items]
Operating Income (Loss)			$ 1,100,000,000
Business Acquisition, Effective Date of Acquisition					Nov. 26, 2018
Business Acquisition, Name of Acquired Entity					Rockwell Collins
Business Acquisition Cash Paid Per Share					$ 93.33
Business Acquisition UTC stock payable					0.37525
Payments to Acquire Businesses, Gross					15,533,000,000
Payments to Acquire Businesses, Net of Cash Acquired					$ 14,900,000,000
Stock Issued During Period, Shares, Acquisitions					62,200,000
Noncash or Part Noncash Acquisition, Debt Assumed					$ 7,800,000,000
Noncash or Part Noncash Acquisition, Value of Assets Acquired					30,600,000,000
Stock Issued During Period, Value, Acquisitions					7,960,000,000
Business Combination, Consideration Transferred					23,493,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents						$ 640,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables						1,665,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory						1,512,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, contract with customer asset, current						291,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other						252,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Noncurrent						38,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment						1,558,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets						1,870,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets						217,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets						16,863,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-term Debt						2,254,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable						520,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, accrued liabilities current						1,657,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, contract with customer liabilities, current						299,000,000
Business Acquisition, Assumed Long-term Debt						5,530,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, liability, defined benefit plan, noncurrent						502,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other						3,464,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, noncontrolling interest						6,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities						14,232,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net						2,631,000,000
Goodwill Resulting from Business Combinations					$ 20,862,000,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net						23,493,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill						10,690,000,000
Fair value adjustment, inventory						282,000,000
Fair value adjustment, fixed assets						256,000,000
Contractual Obligation						1,020,000,000
Rockwell Collins [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles						8,220,000,000
Rockwell Collins [Member] | Customer Relationships [Member] | Maximum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life			20 years
Rockwell Collins [Member] | Customer Relationships [Member] | Minimum [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life			10 years
Rockwell Collins [Member] | Technology-Based Intangible Assets [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles						$ 600,000,000
Finite-Lived Intangible Asset, Useful Life			15 years