Document and Entity Information Document	6 Months Ended
	Jun. 30, 2012	Jul. 30, 2012
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2
Trading Symbol	FRT
Entity Registrant Name	FEDERAL REALTY INVESTMENT TRUST
Entity Central Index Key	0000034903
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		64,111,975