Condensed Combining Financial Information of L3 and Its Subsidiaries- Condensed Combining Statements of Operations (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 29, 2017	Sep. 23, 2016	Sep. 29, 2017	Sep. 23, 2016
Condensed Financial Statements, Captions [Line Items]
Total net sales		$ 2,646	$ 2,505	$ 8,047	$ 7,522
Total cost of sales		(2,396)	(2,290)	(7,232)	(6,808)
Goodwill impairment charge	[1]	(187)	0	(187)	0
Operating income		63	215	628	714
Interest expense		(43)	(41)	(128)	(125)
Interest and other income, net		6	6	15	15
Debt retirement charge				0	(5)
Income from continuing operations before income taxes		26	180	515	599
Provision (benefit) for income taxes		0	(29)	(114)	(130)
Equity in net loss of consolidated subsidiaries		0	0	0	0
Income from continuing operations		26	151	401	469
Loss from discontinued operations, net of income taxes		(1)	0	(1)	63
Net income		25	151	400	532
Net income attributable to noncontrolling interests		(3)	(3)	(12)	(10)
Net income attributable to L3		22	148	388	522
Comprehensive income attributable to L3		85	125	541	529
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales		(83)	(74)	(257)	(204)
Total cost of sales		83	74	257	204
Goodwill impairment charge		0		0
Operating income		0	0	0	0
Interest expense		0	0	0	0
Interest and other income, net		0	0	0	0
Debt retirement charge					0
Income from continuing operations before income taxes		0	0	0	0
Provision (benefit) for income taxes		0	0	0	0
Equity in net loss of consolidated subsidiaries		24	(115)	(268)	(413)
Income from continuing operations		24		(268)	(413)
Loss from discontinued operations, net of income taxes		0		0	0
Net income		24	(115)	(268)	(413)
Net income attributable to noncontrolling interests		(3)	(3)	(12)	(10)
Net income attributable to L3		21	(118)	(280)	(423)
Comprehensive income attributable to L3		(33)	(88)	(407)	(407)
L-3 [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales		840	877	2,603	2,602
Total cost of sales		(746)	(801)	(2,334)	(2,343)
Goodwill impairment charge		0		0
Operating income		94	76	269	259
Interest expense		(42)	(40)	(126)	(124)
Interest and other income, net		7	4	12	10
Debt retirement charge					(5)
Income from continuing operations before income taxes		59	40	155	140
Provision (benefit) for income taxes		(12)	(7)	(34)	(31)
Equity in net loss of consolidated subsidiaries		(24)	115	268	413
Income from continuing operations		23		389	522
Loss from discontinued operations, net of income taxes		(1)		(1)	0
Net income		22	148	388	522
Net income attributable to noncontrolling interests		0	0	0	0
Net income attributable to L3		22	148	388	522
Comprehensive income attributable to L3		85	125	541	529
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales		1,481	1,258	4,500	3,817
Total cost of sales		(1,390)	(1,182)	(4,146)	(3,545)
Goodwill impairment charge		(187)		(187)
Operating income		(96)	76	167	272
Interest expense		0	0	(1)	0
Interest and other income, net		0	0	0	0
Debt retirement charge					0
Income from continuing operations before income taxes		(96)	76	166	272
Provision (benefit) for income taxes		24	(12)	(37)	(59)
Equity in net loss of consolidated subsidiaries		0	0	0	0
Income from continuing operations		(72)		129	213
Loss from discontinued operations, net of income taxes		0		0	63
Net income		(72)	64	129	276
Net income attributable to noncontrolling interests		0	0	0	0
Net income attributable to L3		(72)	64	129	276
Comprehensive income attributable to L3		(67)	64	134	287
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales		408	444	1,201	1,307
Total cost of sales		(343)	(381)	(1,009)	(1,124)
Goodwill impairment charge		0		0
Operating income		65	63	192	183
Interest expense		(1)	(1)	(1)	(1)
Interest and other income, net		(1)	2	3	5
Debt retirement charge					0
Income from continuing operations before income taxes		63	64	194	187
Provision (benefit) for income taxes		(12)	(10)	(43)	(40)
Equity in net loss of consolidated subsidiaries		0	0	0	0
Income from continuing operations		51		151	147
Loss from discontinued operations, net of income taxes		0		0	0
Net income		51	54	151	147
Net income attributable to noncontrolling interests		0	0	0	0
Net income attributable to L3		51	54	151	147
Comprehensive income attributable to L3		$ 100	$ 24	$ 273	$ 120

[1] Represents a goodwill impairment charge recorded during the third quarter of 2017 related to Vertex Aerospace. See Note 8 for additional information.