L-3 Holdings' Earnings Per Common Share (Details) (USD $) Share data in Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 24, 2010	Sep. 24, 2010	Sep. 30, 2011
Reconciliation of net income:
Net income	$ 238,000,000	$ 241,000,000	$ 694,000,000	$ 691,000,000
Net income attributable to noncontrolling interests	(3,000,000)	(3,000,000)	(7,000,000)	(9,000,000)
Net income allocable to participating securities		(1,000,000)	(4,000,000)	(2,000,000)
Net income allocable to L-3 Holdings' common shareholders	235,000,000	237,000,000	683,000,000	680,000,000
Basic:
Weighted average common shares outstanding	103.5	114.0	115.1	106.0
Basic earnings per share:
Net income	$ 2.27	$ 2.08	$ 5.93	$ 6.42
Common and potential common shares:
Weighted average common shares outstanding	103.5	114.0	115.1	106.0
Assumed purchase of common shares for treasury	(2.7)	(3.4)	(3.9)	(3.1)
Assumed conversion of the CODES
Common and potential common shares	104.8	114.7	116.0	107.2
Diluted earning per share:
Net income	$ 2.24	$ 2.07	$ 5.89	$ 6.34
L-3 Holdings' Earnings Per Share (Textuals)
Conversion price of L-3 Holdings' CODES	$ 97.79			$ 97.79
Shares excluded from computation of diluted earnings per share	3.3	3.3	2.7	3.1
Assumed exercise of stock options [Member]
Common and potential common shares:
Common and potential common shares	1.5	2.1	3.0	2.3
Unvested restricted stock awards [Member]
Common and potential common shares:
Common and potential common shares	2.1	1.4	1.3	1.8
Employee stock purchase plan contributions [Member]
Common and potential common shares:
Common and potential common shares	0.4	0.6	0.5	0.1
Performance unit awards [Member]
Common and potential common shares:
Common and potential common shares				0.1