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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% |  |

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