Commitments and Contingencies (Details) (USD $)			3 Months Ended			3 Months Ended	12 Months Ended	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Lexington Avenue Property [Member]	Mar. 31, 2012 Kings Plaza Regional Shopping Center [Member]	Mar. 31, 2012 Paramus Property [Member]	Mar. 31, 2012 Paramus Property [Member] Tenant Occupant [Member] Ikea [Member] acre	Dec. 31, 2021 Paramus Property [Member] Tenant Occupant [Member] Ikea [Member]	Mar. 31, 2012 Flushing Property [Member]	Mar. 31, 2012 General Liability [Member]	Mar. 31, 2012 All Risk Property And Rental Value [Member]	Mar. 31, 2012 Terrorism Coverage Including Nbcr [Member] Self Insured [Member]	Mar. 31, 2012 Reinsurance For Terrorism Coverage Excluding Nbcr [Member] Third Party Carriers [Member]	Mar. 31, 2012 NBCR [Member]
Insurance [Abstract]
Insurance Maximum Coverage Per Incident									$ 300,000,000	$ 1,700,000,000	$ 1,700,000,000	$ 1,700,000,000
Deductible													275,000
Self Insured Responsibility													15.00%
Federal Government Responsibility													85.00%
Mortgage loans, recourse			75,000,000
Mortgage loan, carrying amount	1,327,234,000	1,330,932,000	320,000,000		68,000,000.00
Environmental Remediation [Abstract]
Estimated total costs associated with clean up				2,500,000
Previously Paid Amounts For Environmental Liabilities				500,000
Flushing Property [Abstract]
Non-refundable purchase deposit								1,875,000
Indemnificatiion Sought by Tenant								50,000,000
Loss Contingency, Opinion of Counsel								We believe, after consultation with counsel, that the new claim is without merit.
Loss Contingency, Inestimable Loss								The amount or range of reasonably possible losses, if any, cannot be estimated.
Paramus Property [Abstract]
Acres Of Real Estate Land						30.3
Leases Of Lessor Rental Term Range						40 years
Property purchase option exercisable be leasee							75,000,000.00
Fixed interest rate on the debt					2.90%
Triple-net rent, annual amount						700,000.00
Purchase option exercised, proceeds from sale of land							7,000,000.00
Purchase option excercised, gain on sale of land							62,000,000.00
Purchase Option Not Excercised Amount Included In Triple Net Rent Over Remainder Of Lease							68,000,000.00
Loan Amortization Period							20 years
Letters Of Credit [Abstract]
Standby letters of credit, issued and outstanding	$ 4,998,000.00