Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 26, 2015	Jun. 27, 2014	Jun. 26, 2015	Jun. 27, 2014
Condensed Financial Statements, Captions [Line Items]
Total net sales	$ 2,793	$ 3,019	$ 5,506	$ 5,976
Total cost of sales	(2,629)	(2,780)	(5,120)	(5,451)
(Loss) gain related to business divestitures	2		(20)
Operating (loss) income	166	239	366	525
Interest expense	(48)	(39)	(92)	(82)
Interest and other income, net	5	4	8	9
(Loss) Income before income taxes	123	204	282	452
Benefit (provision) for income taxes	$ 1	$ (63)	(49)	$ (139)
Equity in net income of consolidated subsidiaries
Net income	$ 124	$ 141	233	$ 313
Net income attributable to noncontrolling interests	(4)	(4)	(8)	(6)
Net income attributable to L-3	120	137	225	307
Comprehensive income attributable to L-3	$ 205	$ 169	$ 231	$ 321
L-3 Communications Holdings, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales
Total cost of sales	$ (11)	$ (14)	$ (24)	$ (29)
(Loss) gain related to business divestitures
Operating (loss) income	$ (11)	(14)	$ (24)	(29)
Interest expense		$ 3		$ (2)
Interest and other income, net
(Loss) Income before income taxes	$ (11)	$ (11)	$ (24)	$ (31)
Benefit (provision) for income taxes		3	4	9
Equity in net income of consolidated subsidiaries	$ 131	145	245	329
Net income	$ 120	$ 137	$ 225	$ 307
Net income attributable to noncontrolling interests
Net income attributable to L-3	$ 120	$ 137	$ 225	$ 307
Comprehensive income attributable to L-3	205	169	231	321
L-3 Communications Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales	878	883	1,666	1,746
Total cost of sales	(805)	(798)	(1,523)	(1,567)
(Loss) gain related to business divestitures	(5)		(5)
Operating (loss) income	68	85	138	179
Interest expense	(47)	(38)	(91)	(81)
Interest and other income, net	4	3	7	8
(Loss) Income before income taxes	25	50	54	106
Benefit (provision) for income taxes		(18)	(9)	(33)
Equity in net income of consolidated subsidiaries	95	105	180	234
Net income	$ 120	$ 137	$ 225	$ 307
Net income attributable to noncontrolling interests
Net income attributable to L-3	$ 120	$ 137	$ 225	$ 307
Comprehensive income attributable to L-3	205	169	231	321
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales	1,490	1,655	2,990	3,280
Total cost of sales	(1,465)	(1,552)	(2,853)	(3,033)
(Loss) gain related to business divestitures	$ (25)		(28)
Operating (loss) income		$ 103	109	$ 247
Interest expense	$ (1)		$ (1)
Interest and other income, net
(Loss) Income before income taxes	$ (1)	$ 103	$ 108	$ 247
Benefit (provision) for income taxes	$ 15	$ (31)	$ (19)	$ (76)
Equity in net income of consolidated subsidiaries
Net income	$ 14	$ 72	$ 89	$ 171
Net income attributable to noncontrolling interests
Net income attributable to L-3	$ 14	$ 72	$ 89	$ 171
Comprehensive income attributable to L-3	18	79	90	175
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales	501	555	993	1,098
Total cost of sales	(435)	(504)	(887)	(999)
(Loss) gain related to business divestitures	32		13
Operating (loss) income	$ 98	51	$ 119	99
Interest expense		(1)		(1)
Interest and other income, net	$ 1	1	$ 1	1
(Loss) Income before income taxes	99	51	120	99
Benefit (provision) for income taxes	$ (14)	$ (14)	$ (21)	$ (30)
Equity in net income of consolidated subsidiaries
Net income	$ 85	$ 37	$ 99	$ 69
Net income attributable to noncontrolling interests
Net income attributable to L-3	$ 85	$ 37	$ 99	$ 69
Comprehensive income attributable to L-3	157	60	82	75
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales	(76)	(74)	(143)	(148)
Total cost of sales	$ 87	88	$ 167	177
(Loss) gain related to business divestitures
Operating (loss) income	$ 11	14	$ 24	29
Interest expense		$ (3)		$ 2
Interest and other income, net
(Loss) Income before income taxes	$ 11	$ 11	$ 24	$ 31
Benefit (provision) for income taxes		(3)	(4)	(9)
Equity in net income of consolidated subsidiaries	$ (226)	(250)	(425)	(563)
Net income	(215)	(242)	(405)	(541)
Net income attributable to noncontrolling interests	(4)	(4)	(8)	(6)
Net income attributable to L-3	(219)	(246)	(413)	(547)
Comprehensive income attributable to L-3	$ (380)	$ (308)	$ (403)	$ (571)