Real Estate Partnerships (Details) - Jun. 30, 2015	project property
Schedule of Equity Method Investments
Number of real estate properties owned by partnership | project	90
Federal Realty Investment Trust / ING Clarion Partners Partnership
Schedule of Equity Method Investments
Number of real estate properties owned by partnership	6
Federal Realty Investment Trust | Federal Realty Investment Trust / ING Clarion Partners Partnership
Schedule of Equity Method Investments
Ownership interest in Partnership	30.00%
ING Clarion Partners | Federal Realty Investment Trust / ING Clarion Partners Partnership
Schedule of Equity Method Investments
Ownership interest in Partnership	70.00%