Business Segment Information - Revenues and Income From Continuing Operations by Segment (Details) - USD ($) $ in Millions	3 Months Ended
Apr. 02, 2021	Apr. 03, 2020
Segment Reporting Information [Line Items]
Revenue	$ 4,567	$ 4,626
Income From Continuing Operations Before Income Taxes
L3Harris Merger-related integration expenses	(21)	(31)
Amortization of acquisition-related intangibles	(164)	(145)
Business divestiture-related losses	(15)	(3)
Impairment of goodwill and other assets	(62)	(5)
Pension adjustment	(111)	(97)
Non-operating income	117	95
Net interest expense	(66)	(63)
Income from continuing operations before income taxes	527	221
L3Harris
Income From Continuing Operations Before Income Taxes
Amortization of acquisition-related intangibles	(140)	(120)
Additional cost of sales related to the fair value step-up in inventory sold	0	15
Exelis
Income From Continuing Operations Before Income Taxes
Amortization of acquisition-related intangibles	(24)	(25)
Operating segments \| Integrated Mission Systems
Segment Reporting Information [Line Items]
Revenue	1,451	1,370
Income From Continuing Operations Before Income Taxes
Segment operating income	240	201
Operating segments \| Space and Airborne Systems
Segment Reporting Information [Line Items]
Revenue	1,236	1,192
Income From Continuing Operations Before Income Taxes
Segment operating income	240	221
Operating segments \| Communication Systems
Segment Reporting Information [Line Items]
Revenue	1,112	1,094
Income From Continuing Operations Before Income Taxes
Segment operating income	281	250
Operating segments \| Aviation Systems
Segment Reporting Information [Line Items]
Revenue	814	1,011
Income From Continuing Operations Before Income Taxes
Segment operating income	128	(177)
Corporate eliminations
Segment Reporting Information [Line Items]
Revenue	(46)	(41)
Unallocated corporate expenses
Income From Continuing Operations Before Income Taxes
Segment operating income	(40)	(25)
Divestiture-related expenses	(7)
Accrual for value added tax obligation	$ 15
Additional cost of sales related to the fair value step-up in inventory sold		$ 15

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