Commitments and Contingencies (Details) (USD $)				6 Months Ended		12 Months Ended	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Lexington Avenue Property [Member]	Jun. 30, 2013 Paramus Property [Member] Tenant Occupant [Member] Ikea [Member]	Dec. 31, 2001 Paramus Property [Member] Tenant Occupant [Member] Ikea [Member] acre	Dec. 31, 2021 Paramus Property [Member] Tenant Occupant [Member] Ikea [Member] Scenario, Forecast [Member]	Jun. 30, 2013 Flushing Property [Member]	Jun. 30, 2013 General Liability [Member]	Jun. 30, 2013 All Risk Property And Rental Value [Member]	Jun. 30, 2013 Terrorism Coverage Including Nbcr [Member]	Jun. 30, 2013 NBCR [Member]
Insurance [Abstract]
Insurance Maximum Coverage Per Incident								$ 300,000,000	$ 1,700,000,000	$ 1,700,000,000
Deductible											275,000
Self Insured Responsibility											15.00%
Federal Government Responsibility											85.00%
Mortgage Loan Converted To Recourse (in US Dollars)			75,000,000
Mortgage payable (in US Dollars)	1,058,028,000	1,065,916,000	320,000,000	68,000,000
Flushing Property [Abstract]
Non-refundable purchase deposit							1,875,000
Indemnification Sought by Tenant							50,000,000
Paramus Property [Abstract]
Acres Of Land					30.3
Leases Of Lessor Rental Term Range				40 years
Property purchase option exercisable by lessee						75,000,000
Fixed interest rate on the debt				2.90%
Triple-net rent, annual amount				700,000
Purchase option exercised, proceeds from sale of land						7,000,000
Purchase option exercised, gain on sale of land						60,000,000
Purchase option not exercised, amount included in triple net rent over remainder of lease						68,000,000
Loan Amortization Period						20 years
Letters Of Credit [Abstract]
Standby letters of credit, issued and outstanding	$ 4,058,000