Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ in Thousands				3 Months Ended			12 Months Ended
	Nov. 19, 2015	Apr. 24, 2015	Jul. 24, 2014	Dec. 31, 2015	Jun. 30, 2015	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of real estate							$ 28,330	$ 4,401	$ 4,994
Federal Realty Investment Trust/Clarion Partners Partnership
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of real estate			$ 14,500				$ 0	$ 14,507	$ 0
Federal Realty Investment Trust | Federal Realty Investment Trust/Clarion Partners Partnership
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of real estate			$ 4,400			$ 4,400
Houston Street
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of real estate		$ 11,500			$ 11,500
Courtyard Shops
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of real estate	$ 16,800			$ 16,800