Debt - Components of Debt and Reconciliation to Carrying Amount of Long-Term Debt (Parenthetical) (Detail) (USD $)	3 Months Ended											3 Months Ended
	Mar. 29, 2013	Dec. 31, 2012	Mar. 29, 2013 CODES due 2035 [Member]	Mar. 29, 2013 L-3 Communications Corporation's [Member] 3.95% Senior Notes due 2016 [Member]	Dec. 31, 2012 L-3 Communications Corporation's [Member] 3.95% Senior Notes due 2016 [Member]	Mar. 29, 2013 L-3 Communications Corporation's [Member] 5.20% Senior Notes due 2019 [Member]	Dec. 31, 2012 L-3 Communications Corporation's [Member] 5.20% Senior Notes due 2019 [Member]	Mar. 29, 2013 L-3 Communications Corporation's [Member] 4.75% Senior Notes due 2020 [Member]	Dec. 31, 2012 L-3 Communications Corporation's [Member] 4.75% Senior Notes due 2020 [Member]	Mar. 29, 2013 L-3 Communications Corporation's [Member] 4.95% Senior Notes due 2021 [Member]	Dec. 31, 2012 L-3 Communications Corporation's [Member] 4.95% Senior Notes due 2021 [Member]	Mar. 29, 2013 L-3 Communications Holdings, Inc. [Member]	Mar. 30, 2012 L-3 Communications Holdings, Inc. [Member]	Mar. 29, 2013 L-3 Communications Holdings, Inc. [Member] CODES due 2035 [Member]	Dec. 31, 2012 L-3 Communications Holdings, Inc. [Member] CODES due 2035 [Member]	May 31, 2013 L-3 Communications Holdings, Inc. [Member] Subsequent event [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes			3.00%	3.95%	3.95%	5.20%	5.20%	4.75%	4.75%	4.95%	4.95%			3.00%	3.00%
Borrowings under Amended and Restated Revolving Credit Facility	$ 1,000,000,000
Revolving Credit Facility expiry date	Feb. 03, 2017
Excess of current common stock price over common stock conversion price	120.00%
Common stock, shares	7,600,000
Current convertible common stock price														$ 109.45
Conversion price of L-3 Holdings' CODES	$ 91.21													$ 91.21
Closing stock price																$ 83.42
Interest expense recognized												5,000,000	5,000,000
Carrying amount of the equity component (conversion feature)	$ 64,000,000	$ 64,000,000