Document and Entity Information (USD $) In Billions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Feb. 19, 2014	Jun. 28, 2013
Document And Entity Information [Abstract]
Document Type	10-K/A
Amendment Flag	true
Amendment Description	We are filing this Amendment No. 1 (this “Amendment” or “Form 10-K/A”) to our Annual Report on Form 10-K for the fiscal year ended December 31, 2013 following the completion of the internal review of our Aerospace Systems segment, which is discussed in our document.
Document Period End Date	Dec. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY
Trading Symbol	LLL
Entity Registrant Name	L 3 COMMUNICATIONS HOLDINGS INC
Entity Central Index Key	0001056239
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		85,847,821
Entity Public Float			$ 7.6