Business Segment Information - Revenues and Income From Continuing Operations by Segment (Details) - USD ($)	3 Months Ended			9 Months Ended
	Oct. 02, 2020	Jul. 03, 2020	Sep. 27, 2019	Oct. 02, 2020	Sep. 27, 2019
Segment Reporting Information [Line Items]
Revenue	$ 4,463,000,000		$ 4,431,000,000	$ 13,534,000,000	$ 8,024,000,000
Income From Continuing Operations Before Income Taxes
L3Harris Merger-related transaction and integration expenses	(27,000,000)		(170,000,000)	(95,000,000)	(222,000,000)
Restructuring charges				(24,000,000)
Amortization of acquisition-related intangibles	(179,000,000)		(125,000,000)	(546,000,000)	(181,000,000)
Business divestiture-related (losses) gains	(10,000,000)		229,000,000	(62,000,000)	229,000,000
Pension adjustment	(97,000,000)		(80,000,000)	(292,000,000)	(173,000,000)
Non-operating income	96,000,000		79,000,000	296,000,000	173,000,000
Net interest expense	(62,000,000)		(58,000,000)	(190,000,000)	(139,000,000)
Income from continuing operations before income taxes	518,000,000		440,000,000	1,075,000,000	1,025,000,000
Non-cash goodwill impairment charge			0	369,000,000
L3Harris and Exelis
Income From Continuing Operations Before Income Taxes
Amortization of acquisition-related intangibles	(176,000,000)		(123,000,000)	(529,000,000)	(173,000,000)
L3Harris
Segment Reporting Information [Line Items]
Revenue					8,024,000,000
Income From Continuing Operations Before Income Taxes
Restructuring charges	0	$ (7,000,000)	(111,000,000)	(7,000,000)	(111,000,000)
Amortization of acquisition-related intangibles	(151,000,000)		(98,000,000)	(454,000,000)	(98,000,000)
Additional costs of sale related to fair value step-up in inventory sold	0		92,000,000	31,000,000	92,000,000
Exelis
Income From Continuing Operations Before Income Taxes
Amortization of acquisition-related intangibles	(25,000,000)		(25,000,000)	(75,000,000)	(75,000,000)
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income From Continuing Operations Before Income Taxes
Business divestiture-related (losses) gains				(296,000,000)
Integrated Mission Systems
Income From Continuing Operations Before Income Taxes
Non-cash goodwill impairment charge				0
Space and Airborne Systems
Income From Continuing Operations Before Income Taxes
Non-cash goodwill impairment charge				5,000,000
Communication Systems
Income From Continuing Operations Before Income Taxes
Non-cash goodwill impairment charge				0
Aviation Systems
Income From Continuing Operations Before Income Taxes
Non-cash goodwill impairment charge				364,000,000
Operating segments | Integrated Mission Systems
Segment Reporting Information [Line Items]
Revenue	1,372,000,000		1,292,000,000	4,073,000,000	1,317,000,000
Income From Continuing Operations Before Income Taxes
Segment operating income	213,000,000		176,000,000	638,000,000	182,000,000
Operating segments | Space and Airborne Systems
Segment Reporting Information [Line Items]
Revenue	1,249,000,000		1,173,000,000	3,690,000,000	3,148,000,000
Income From Continuing Operations Before Income Taxes
Segment operating income	231,000,000		230,000,000	687,000,000	599,000,000
Operating segments | Communication Systems
Segment Reporting Information [Line Items]
Revenue	1,094,000,000		1,032,000,000	3,300,000,000	2,221,000,000
Income From Continuing Operations Before Income Taxes
Segment operating income	273,000,000		234,000,000	788,000,000	577,000,000
Operating segments | Aviation Systems
Segment Reporting Information [Line Items]
Revenue	792,000,000		948,000,000	2,603,000,000	1,278,000,000
Income From Continuing Operations Before Income Taxes
Segment operating income	100,000,000		127,000,000	(46,000,000)	163,000,000
Operating segments | Other non-reportable business segments
Segment Reporting Information [Line Items]
Revenue	0		23,000,000	0	102,000,000
Income From Continuing Operations Before Income Taxes
Segment operating income	0		0	0	14,000,000
Corporate eliminations
Segment Reporting Information [Line Items]
Revenue	(44,000,000)		(37,000,000)	(132,000,000)	(42,000,000)
Unallocated corporate expenses
Income From Continuing Operations Before Income Taxes
Segment operating income	(23,000,000)		(93,000,000)	(113,000,000)	(94,000,000)
Divestiture-related expenses	$ 2,000,000			11,000,000
Non-cash cumulative adjustment to lease expense			12,000,000		12,000,000
Unallocated corporate expenses | L3Harris
Income From Continuing Operations Before Income Taxes
Additional costs of sale related to fair value step-up in inventory sold			92,000,000	31,000,000	92,000,000
Unallocated corporate expenses | Disposal Group, Held-for-sale, Not Discontinued Operations
Income From Continuing Operations Before Income Taxes
Non-cash goodwill impairment charge				14,000,000
Unallocated corporate expenses | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income From Continuing Operations Before Income Taxes
Gain on sale of asset group			$ 12,000,000		$ 12,000,000
Unallocated corporate expenses | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Applied Kilovolts and Analytical Instrumentation Business
Income From Continuing Operations Before Income Taxes
Non-cash goodwill impairment charge				$ 5,000,000