Real Estate Partnership (Summarized Operating Results and Financial Position of Partnership) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Real Estate Partnership Operating Results [Line Items]
Revenue	$ 167,947	$ 157,388	$ 338,775	$ 314,537
Depreciation and amortization	40,893	39,757	84,743	80,274
Interest expense	23,213	27,147	46,350	54,552
NET INCOME	45,416	38,797	85,961	74,639
Our share of net income from real estate partnership	250	372	463	684
Real estate, net	4,060,187		4,060,187		3,798,992
Cash	41,312	108,366	41,312	108,366	88,927	36,988
TOTAL ASSETS	4,431,485		4,431,485		4,219,294
Mortgages payable	634,045		634,045		588,456
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	4,431,485		4,431,485		4,219,294
Our investment in real estate partnership	35,511		35,511		32,264
Federal / Lion Venture LP [Member]
Real Estate Partnership Operating Results [Line Items]
Revenue	4,469	4,624	9,487	9,573
Other operating expenses	1,390	1,318	3,500	3,135
Depreciation and amortization	1,590	1,361	3,077	2,730
Interest expense	781	841	1,620	1,683
Total expenses	3,761	3,520	8,197	7,548
NET INCOME	708	1,104	1,290	2,025
Real estate, net	169,193		169,193		170,867
Cash	3,046		3,046		2,210
Other assets	5,170		5,170		5,668
TOTAL ASSETS	177,409		177,409		178,745
Mortgages payable	44,885		44,885		56,922
Other liabilities	3,937		3,937		4,100
Partners' capital	128,587		128,587		117,723
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	177,409		177,409		178,745
Federal Realty Investment Trust [Member] | Federal / Lion Venture LP [Member]
Real Estate Partnership Operating Results [Line Items]
Our share of net income from real estate partnership	250	372	463	684
Our share of unconsolidated debt	13,466		13,466		17,077
Our investment in real estate partnership	$ 35,511		$ 35,511		$ 32,264