Acquisitions, Dispositions, Goodwill and Other Intangible Assets (General Information) (Details) - USD ($) shares in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Nov. 26, 2018
Business Acquisition [Line Items]
Acquisition Cost Of Acquired Entities and Interest in Affiliates	$ 19,000,000
Proceeds from Issuance of Debt			$ 11,000,000,000
Proceeds from Debt, Net of Issuance Costs			$ 10,900,000,000
Goodwill Resulting from Business Combinations	93,000,000
Contractual Obligation, Due in Next Fiscal Year	145,000,000
Contractual Obligation, Due in Second Year	133,000,000
Contractual Obligation, Due in Third Year	131,000,000
Contractual Obligation, Due in Fourth Year	125,000,000
Contractual Obligation, Due in Fifth Year	118,000,000
Business Combination, Acquisition Related Costs	$ 9,000,000	$ 30,000,000
Rockwell Collins [Member]
Business Acquisition [Line Items]
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			15,500,000,000
Payments to Acquire Businesses, Net of Cash Acquired			$ 14,900,000,000
Stock Issued During Period, Shares, Acquisitions			62.2
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				1,663,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory				1,520,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, contract with customer asset, current				301,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other				264,000,000
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				1,691,000,000
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				210,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets				17,117,000,000
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				378,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, accrued liabilities current				1,689,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, contract with customer liabilities, current				301,000,000
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				3,517,000,000
Business combination, recognized identifiable assets acquired and liabilities assumed, noncontrolling interest				6,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities				14,177,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net				2,940,000,000
Goodwill Resulting from Business Combinations			$ 20,553,000,000
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				10,790,000,000
Fair value adjustment, inventory				282,000,000
Fair value adjustment, fixed assets				269,000,000
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				8,320,000,000
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