Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Equity (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 25, 2015	Jun. 26, 2015	Mar. 27, 2015	Dec. 31, 2014	Sep. 26, 2014	Jun. 27, 2014	Mar. 28, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				$ 5,360				$ 6,056	$ 5,360	$ 6,056	$ 5,527
Net income (loss) attributable to L-3	$ (166)	$ (299)	$ 120	105	$ 203	$ 154	$ 137	170	(240)	664	751
Comprehensive income (loss)									10	(474)	440
Other									9	8	11
Ending Balance	4,429				5,360				4,429	5,360	6,056
Common Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				$ 1				$ 1	$ 1	$ 1	$ 1
Beginning Balance, Shares				82,000,000				85,800,000	82,000,000	85,800,000	90,400,000
Ending Balance	$ 1				$ 1				$ 1	$ 1	$ 1
Ending Balance, Shares	78,100,000				82,000,000				78,100,000	82,000,000	85,800,000
Additional Paid-in Capital [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				$ 5,798				$ 5,652	$ 5,798	$ 5,652	$ 5,313
Other									9	8	10
Ending Balance	$ 6,051				$ 5,798				6,051	5,798	5,652
Retained Earnings [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				6,181				5,726	6,181	5,726	5,175
Other											1
Ending Balance	5,728				6,181				5,728	6,181	5,726
Accumulated Other Comprehensive Loss [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				(584)				(110)	(584)	(110)	(550)
Comprehensive income (loss)									10	(474)	440
Ending Balance	(574)				(584)				(574)	(584)	(110)
L-3 Communications Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				$ 5,285				$ 5,981	5,285	5,981	5,451
Net income (loss) attributable to L-3									(240)	664	751
Contributions from L-3 Holdings									253	146	339
Dividends to L-3 Holdings									(953)	(1,032)	(1,001)
Comprehensive income (loss)									10	(474)	440
Other											1
Ending Balance	$ 4,355				$ 5,285				$ 4,355	$ 5,285	$ 5,981
L-3 Communications Corporation [Member] | Common Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance, Shares				100				100	100	100	100
Ending Balance, Shares	100				100				100	100	100
L-3 Communications Corporation [Member] | Additional Paid-in Capital [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				$ 5,799				$ 5,653	$ 5,799	$ 5,653	$ 5,314
Contributions from L-3 Holdings									253	146	339
Ending Balance	$ 6,052				$ 5,799				6,052	5,799	5,653
L-3 Communications Corporation [Member] | Retained Earnings [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				70				438	70	438	687
Net income (loss) attributable to L-3									(240)	664	751
Dividends to L-3 Holdings									(953)	(1,032)	(1,001)
Other											1
Ending Balance	(1,123)				70				(1,123)	70	438
L-3 Communications Corporation [Member] | Accumulated Other Comprehensive Loss [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				$ (584)				$ (110)	(584)	(110)	(550)
Comprehensive income (loss)									10	(474)	440
Ending Balance	$ (574)				$ (584)				$ (574)	$ (584)	$ (110)