Document and Entity Information	6 Months Ended
	Jun. 29, 2012	Jul. 27, 2012
Document and Entity Information [Abstract]
Entity Registrant Name	L 3 COMMUNICATIONS HOLDINGS INC
Entity Central Index Key	0001056239
Document Type	10-Q
Document Period End Date	Jun. 29, 2012
Amendment Flag	false
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		96,554,031