Summary Of Significant Accounting Policies (Variable Interest Entities) (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 16, 2006	Dec. 31, 2015	Oct. 16, 2023	Oct. 16, 2021	Oct. 01, 2015	May. 04, 2015	Feb. 25, 2015	Dec. 31, 2014	Dec. 30, 2011
Variable Interest Entity [Line Items]
Mortgages payable		$ 482,822						$ 563,698
Real estate, net		4,490,365						4,141,948
Melville Mall
Variable Interest Entity [Line Items]
Master lease term	20 years
Real estate, net		65,000						61,900
Melville Mall | Scenario, Forecast
Variable Interest Entity [Line Items]
Purchase price under option			$ 5,000	$ 5,000
Plaza El Segundo
Variable Interest Entity [Line Items]
Mortgages payable		178,300						180,300
Real estate, net		172,200						178,100
Ownership percentage									48.20%
Real Estate Maximum Exposure to Loss		19,500
The Grove at Shrewsbury (East)
Variable Interest Entity [Line Items]
Mortgages payable								7,400
Real estate, net								15,700
Price to acquire non controlling interest							$ 8,800
CocoWalk
Variable Interest Entity [Line Items]
Real estate, net		97,200
Real Estate Maximum Exposure to Loss		88,800
Common interest percentage						80.00%
The Shops at Sunset Place
Variable Interest Entity [Line Items]
Mortgages payable		75,900
Real estate, net		115,800
Real Estate Maximum Exposure to Loss		$ 35,500
Common interest percentage					85.00%
Second Mortgage | Melville Mall
Variable Interest Entity [Line Items]
Mortgages payable	$ 34,200
Darien
Variable Interest Entity [Line Items]
Maximum period of sale to defer gain on sale of other property, days		180 days
Federal Realty Investment Trust/Clarion Partners Partnership
Variable Interest Entity [Line Items]
Mortgages payable		$ 34,385						34,385
Real estate, net		$ 146,906						$ 149,203
Federal Realty Investment Trust/Clarion Partners Partnership | Clarion
Variable Interest Entity [Line Items]
Ownership percentage in partnership		70.00%