Unaudited Quarterly Financial Data - Company's Unaudited Quarterly Results of Operations (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 27, 2013	Jun. 28, 2013	Mar. 29, 2013	Dec. 31, 2012	Sep. 28, 2012	Jun. 29, 2012	Mar. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Sales	$ 3,234	$ 3,002	$ 3,189	$ 3,197	$ 3,520	$ 3,284	$ 3,143	$ 3,160
Operating income	306	306	290	310	339	319	328	322	1,212	1,308	1,398
Income from continuing operations	188	204	176	192	199	188	189	186	760	762	866
Net income attributable to L-3	$ 185	$ 200	$ 175	$ 191	$ 196	$ 185	$ 203	$ 200	$ 751	$ 784	$ 958
Basic EPS from continuing operations					$ 2.11	$ 1.94	$ 1.93	$ 1.88	$ 8.40	$ 7.85	$ 8.19
Diluted EPS from continuing operations					$ 2.08	$ 1.91	$ 1.91	$ 1.86	$ 8.24	$ 7.74	$ 8.10
Basic EPS	$ 2.10	$ 2.23	$ 1.95	$ 2.12	$ 2.11	$ 1.93	$ 2.09	$ 2.02	$ 8.40	$ 8.14	$ 9.16
Diluted EPS	$ 2.04	$ 2.19	$ 1.92	$ 2.09	$ 2.08	$ 1.90	$ 2.06	$ 2.00	$ 8.24	$ 8.03	$ 9.05