Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 3,208	$ 2,940	$ 3,019	$ 2,957	$ 3,234	$ 3,002	$ 3,189	$ 3,197	$ 12,124	$ 12,622	$ 13,107
Cost of sales									(11,039)	(11,410)	(11,799)
Operating (loss) income	303	257	239	286	306	306	290	310	1,085	1,212	1,308
Interest expense									(178)	(177)	(184)
Interest and other income (expense), net									18	20	11
Debt Retirement Charge											(13)
(Loss) income from continuing operations before income taxes									925	1,055	1,122
Benefit (provision) for income taxes									(248)	(295)	(360)
Equity in net income of consolidated subsidiaries
Income from continuing operations									677	760	762
Income from discontinued operations, net of income tax											32
Net income	207	157	141	172	188	204	176	192	677	760	794
Net income attributable to noncontrolling interests									(13)	(9)	(10)
Net income attributable to L-3	203	154	137	170	185	200	175	191	664	751	784
Comprehensive income attributable to L-3									190	1,191	688
L-3 Communications Holdings, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales
Cost of sales									(52)	(59)	(59)
Operating (loss) income									(52)	(59)	(59)
Interest expense									(2)	(21)	(21)
Interest and other income (expense), net
Debt Retirement Charge
(Loss) income from continuing operations before income taxes									(54)	(80)	(80)
Benefit (provision) for income taxes									14	22	26
Equity in net income of consolidated subsidiaries									704	809	838
Income from continuing operations											784
Income from discontinued operations, net of income tax
Net income									664	751	784
Net income attributable to noncontrolling interests
Net income attributable to L-3									664	751	784
Comprehensive income attributable to L-3									190	1,191	688
L-3 Communications Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales									3,556	3,842	3,737
Cost of sales									(3,211)	(3,549)	(3,434)
Operating (loss) income									345	293	303
Interest expense									(176)	(176)	(183)
Interest and other income (expense), net									15	15	14
Debt Retirement Charge											(13)
(Loss) income from continuing operations before income taxes									184	132	121
Benefit (provision) for income taxes									(49)	(38)	(37)
Equity in net income of consolidated subsidiaries									529	657	668
Income from continuing operations											752
Income from discontinued operations, net of income tax											32
Net income									664	751	784
Net income attributable to noncontrolling interests
Net income attributable to L-3									664	751	784
Comprehensive income attributable to L-3									190	1,191	688
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales									6,618	6,804	7,475
Cost of sales									(6,117)	(6,139)	(6,749)
Operating (loss) income									501	665	726
Interest expense									(2)
Interest and other income (expense), net											(5)
Debt Retirement Charge
(Loss) income from continuing operations before income taxes									499	665	721
Benefit (provision) for income taxes									(134)	(184)	(230)
Equity in net income of consolidated subsidiaries
Income from continuing operations											491
Income from discontinued operations, net of income tax
Net income									365	481	491
Net income attributable to noncontrolling interests
Net income attributable to L-3									365	481	491
Comprehensive income attributable to L-3									363	480	493
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales									2,256	2,363	2,278
Cost of sales									(2,017)	(2,109)	(1,999)
Operating (loss) income									239	254	279
Interest expense										(1)	(1)
Interest and other income (expense), net									3	5	2
Debt Retirement Charge
(Loss) income from continuing operations before income taxes									242	258	280
Benefit (provision) for income taxes									(65)	(73)	(93)
Equity in net income of consolidated subsidiaries
Income from continuing operations											187
Income from discontinued operations, net of income tax
Net income									177	185	187
Net income attributable to noncontrolling interests
Net income attributable to L-3									177	185	187
Comprehensive income attributable to L-3									46	159	215
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales									(306)	(387)	(383)
Cost of sales									358	446	442
Operating (loss) income									52	59	59
Interest expense									2	21	21
Interest and other income (expense), net
Debt Retirement Charge
(Loss) income from continuing operations before income taxes									54	80	80
Benefit (provision) for income taxes									(14)	(22)	(26)
Equity in net income of consolidated subsidiaries									(1,233)	(1,466)	(1,506)
Income from continuing operations											(1,452)
Income from discontinued operations, net of income tax
Net income									(1,193)	(1,408)	(1,452)
Net income attributable to noncontrolling interests									(13)	(9)	(10)
Net income attributable to L-3									(1,206)	(1,417)	(1,462)
Comprehensive income attributable to L-3									$ (599)	$ (1,830)	$ (1,396)