Commitments and Contingencies (Details) (USD $)			12 Months Ended		12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Lexington Avenue Property [Member]	Dec. 31, 2012 Paramus Property [Member]	Dec. 31, 2021 Paramus Property [Member] Tenant Occupant [Member] Ikea [Member]	Dec. 31, 2012 Paramus Property [Member] Tenant Occupant [Member] Ikea [Member] acre	Dec. 31, 2002 Flushing Property [Member]	Dec. 31, 2012 Flushing Property [Member] New World Mall Llc [Member]	Dec. 31, 2012 General Liability [Member]	Dec. 31, 2012 All Risk Property And Rental Value [Member]	Dec. 31, 2012 Terrorism Coverage Including Nbcr [Member] Self Insured [Member]	Dec. 31, 2012 Reinsurance For Terrorism Coverage Excluding Nbcr [Member] Third Party Carriers [Member]	Dec. 31, 2012 NBCR [Member]
Insurance [Abstract]
Mortgage loans, recourse			$ 75,000,000
Mortgages payable	1,065,916,000	1,080,932,000	320,000,000	68,000,000.00
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%
Flushing Property [Abstract]
Non-refundable purchase deposit							1,875,000
Loss Contingency, Damages Sought, Value								50,000,000
Paramus Property [Abstract]
Area Of Land						30.3
Leases Of Lessor Rental Term Range						40 years
Property purchase option exercisable be leasee with purchase option in 2021					75,000,000.00
Mortgages payable	1,065,916,000	1,080,932,000	320,000,000	68,000,000.00
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					60,000,000.00
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	$ 4,058,000.00