Commitments and Contingencies (Details)			1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 15, 2015 USD ($)	Jun. 24, 2014 USD ($)	Feb. 28, 2014 Fires	Dec. 31, 2015 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2015 USD ($)	Jan. 31, 2016 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2001 a
Paramus Property [Abstract]
Mortgages payable, net of deferred debt issuance costs				$ 1,053,262,000		$ 1,053,262,000		$ 1,027,956,000
Letters Of Credit [Abstract]
Standby letters of credit, outstanding				2,074,000		2,074,000
Letters Of Credit Issued				2,074,000		2,074,000
Kings Plaza Regional Shopping Center [Member]
Loss Contingency [Abstract]
Loss Contingency, Damages Sought, Value	$ 20,300,000
Paramus Property [Member] | Tenant Occupant [Member] | Ikea [Member]
Paramus Property [Abstract]
Area Of Land (in acre) | a									30.3
Mortgages payable, net of deferred debt issuance costs				$ 68,000,000		$ 68,000,000
Fixed interest rate on the debt (in percentage)				2.90%		2.90%
Debt Instrument Maturity Date String						October 2018
Triple-net rent, annual amount						$ 700,000
Paramus Property [Member] | Tenant Occupant [Member] | Ikea [Member] | Scenario Forecast [Member]
Paramus Property [Abstract]
Property purchase option exercisable be leasee with purchase option in 2021					$ 75,000,000
Purchase option exercised, net cash proceeds from sale of land					7,000,000
Purchase option excercised, gain on sale of land					60,000,000
Purchase option not excercised amount included in triple net rent over remainder of lease					$ 68,000,000
Loan Amortization Period					20 years
Rego Park I [Member]
Loss Contingency [Abstract]
Proceeds from Legal Settlements				$ 2,100,000
Rego Park I [Member] | Sears [Member]
Loss Contingency [Abstract]
Number Of Fires | Fires			2
Rego Park I [Member] | Sears [Member] | Minimum [Member]
Loss Contingency [Abstract]
Loss Contingency, Damages Sought, Value		$ 4,000,000
Rego Park I [Member] | Sears [Member] | Minimum [Member] | Estimated Future Damages [Member]
Loss Contingency [Abstract]
Loss Contingency, Damages Sought, Value		$ 25,000,000
General Liability [Member]
Insurance [Abstract]
Insurance Maximum Coverage Per Incident						300,000,000
All Risk Property And Rental Value [Member]
Insurance [Abstract]
Insurance Maximum Coverage Per Incident						1,700,000,000
Terrorism Coverage Including Nbcr [Member]
Insurance [Abstract]
Insurance Maximum Coverage Per Incident						1,700,000,000
Insurance Maximum Coverage In Aggregate						1,700,000,000
NBCR [Member]
Insurance [Abstract]
Deductible				$ 275,000		$ 275,000
Self Insured Responsibility (in percentage)				15.00%		15.00%
Federal Government Responsibility (in percentage)				85.00%		85.00%
NBCR [Member] | Subsequent Event [Member]
Insurance [Abstract]
Deductible							$ 348,000
Self Insured Responsibility (in percentage)							16.00%
Federal Government Responsibility (in percentage)							84.00%