Condensed Combining Financial Information of L3 and Its Subsidiaries - Financial Statement Revisions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Total assets	$ 13,530		$ 13,530		$ 12,730	$ 12,729
Total liabilities	8,018		8,018		7,566	7,578
Total equity	5,512	$ 5,047	5,512	$ 5,047	$ 5,164	5,151	$ 4,624
Net income	379	207	587	375
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets	(12,297)		(12,297)			(11,982)
Total liabilities	(441)		(441)			(401)
Total equity	(11,856)		(11,856)			(11,581)
Net income	(221)	(191)	(411)	(336)
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets	11,763		11,763			11,471
Total liabilities	1,621		1,621			1,578
Total equity	10,142		10,142			9,893
Net income	159	145	280	248
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets	2,955		2,955			2,781
Total liabilities	1,173		1,173			1,025
Total equity	1,782		1,782			1,756
Net income	$ 66	51	$ 140	97
As Reported [Member] | Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets						(10,930)
Total liabilities						(419)
Total equity						(10,511)
Net income		(164)		(292)
As Reported [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets						10,270
Total liabilities						1,756
Total equity						8,514
Net income		117		201
As Reported [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets						3,156
Total liabilities						1,091
Total equity						2,065
Net income		52		100
Adjustment [Member] | Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets						(1,052)
Total liabilities						18
Total equity						(1,070)
Net income		(27)		(44)
Adjustment [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets						1,201
Total liabilities						(178)
Total equity						1,379
Net income		28		47
Adjustment [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total assets						(375)
Total liabilities						(66)
Total equity						$ (309)
Net income		$ (1)		$ (3)