Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 25, 2015	Sep. 26, 2014	Sep. 25, 2015	Sep. 26, 2014
Condensed Financial Statements, Captions [Line Items]
Total net sales	$ 2,817	$ 2,940	$ 8,323	$ 8,916
Total cost of sales	(2,531)	(2,683)	(7,651)	(8,134)
(Loss) gain related to business divestitures	(9)		(29)
Impairment charge	(491)		(491)
Operating (loss) income	(214)	257	152	782
Interest expense	(47)	(47)	(139)	(129)
Interest and other income, net	3	5	11	14
(Loss) income before income taxes	(258)	215	24	667
Benefit (provision) for income taxes	$ (38)	$ (58)	$ (87)	$ (197)
Equity in net (loss) income of consolidated subsidiaries
Net (loss) income	$ (296)	$ 157	$ (63)	$ 470
Net income attributable to noncontrolling interests	(3)	(3)	(11)	(9)
Net (loss) income attributable to L-3	(299)	154	(74)	461
Comprehensive income (loss) attributable to L-3	$ (351)	$ 90	$ (120)	$ 411
L-3 Communications Holdings, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales
Total cost of sales	$ (12)	$ (10)	$ (36)	$ (39)
(Loss) gain related to business divestitures
Impairment charge
Operating (loss) income	$ (12)	$ (10)	$ (36)	(39)
Interest expense				$ (2)
Interest and other income, net
(Loss) income before income taxes	$ (12)	$ (10)	$ (36)	$ (41)
Benefit (provision) for income taxes	7	3	11	12
Equity in net (loss) income of consolidated subsidiaries	(294)	161	(49)	490
Net (loss) income	$ (299)	$ 154	$ (74)	$ 461
Net income attributable to noncontrolling interests
Net (loss) income attributable to L-3	$ (299)	$ 154	$ (74)	$ 461
Comprehensive income (loss) attributable to L-3	(351)	90	(120)	411
L-3 Communications Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales	873	860	2,539	2,606
Total cost of sales	(790)	(787)	(2,313)	(2,354)
(Loss) gain related to business divestitures	$ (8)		$ (13)
Impairment charge
Operating (loss) income	$ 75	73	$ 213	252
Interest expense	(47)	(46)	(138)	(127)
Interest and other income, net	2	4	9	12
(Loss) income before income taxes	30	31	84	137
Benefit (provision) for income taxes	(10)	(8)	(19)	(41)
Equity in net (loss) income of consolidated subsidiaries	(319)	131	(139)	365
Net (loss) income	$ (299)	$ 154	$ (74)	$ 461
Net income attributable to noncontrolling interests
Net (loss) income attributable to L-3	$ (299)	$ 154	$ (74)	$ 461
Comprehensive income (loss) attributable to L-3	(351)	90	(120)	411
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales	1,584	1,628	4,574	4,908
Total cost of sales	(1,442)	(1,500)	(4,295)	(4,533)
(Loss) gain related to business divestitures	(1)		(29)
Impairment charge	(491)		(491)
Operating (loss) income	$ (350)	128	(241)	375
Interest expense		$ (2)	$ (1)	$ (2)
Interest and other income, net
(Loss) income before income taxes	$ (350)	$ 126	$ (242)	$ 373
Benefit (provision) for income taxes	$ (14)	$ (34)	$ (33)	$ (110)
Equity in net (loss) income of consolidated subsidiaries
Net (loss) income	$ (364)	$ 92	$ (275)	$ 263
Net income attributable to noncontrolling interests
Net (loss) income attributable to L-3	$ (364)	$ 92	$ (275)	$ 263
Comprehensive income (loss) attributable to L-3	(370)	89	(280)	264
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales	449	525	1,442	1,623
Total cost of sales	$ (388)	(469)	(1,275)	(1,468)
(Loss) gain related to business divestitures			$ 13
Impairment charge
Operating (loss) income	$ 61	56	$ 180	$ 155
Interest expense		1
Interest and other income, net	$ 1	1	$ 2	$ 2
(Loss) income before income taxes	62	58	182	157
Benefit (provision) for income taxes	$ (14)	$ (16)	$ (35)	$ (46)
Equity in net (loss) income of consolidated subsidiaries
Net (loss) income	$ 48	$ 42	$ 147	$ 111
Net income attributable to noncontrolling interests
Net (loss) income attributable to L-3	$ 48	$ 42	$ 147	$ 111
Comprehensive income (loss) attributable to L-3	(9)	(22)	73	53
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales	(89)	(73)	(232)	(221)
Total cost of sales	$ 101	83	$ 268	260
(Loss) gain related to business divestitures
Impairment charge
Operating (loss) income	$ 12	$ 10	$ 36	39
Interest expense				$ 2
Interest and other income, net
(Loss) income before income taxes	$ 12	$ 10	$ 36	$ 41
Benefit (provision) for income taxes	(7)	(3)	(11)	(12)
Equity in net (loss) income of consolidated subsidiaries	613	(292)	188	(855)
Net (loss) income	618	(285)	213	(826)
Net income attributable to noncontrolling interests	(3)	(3)	(11)	(9)
Net (loss) income attributable to L-3	615	(288)	202	(835)
Comprehensive income (loss) attributable to L-3	$ 730	$ (157)	$ 327	$ (728)