Investments in Partially Owned Entities (Details 1) (USD $) In Thousands, unless otherwise specified											0 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2012 Land [Member]	Dec. 21, 2012 Land [Member]	Dec. 31, 2012 Building Improvements [Member]	Dec. 21, 2012 Building Improvements [Member]	Dec. 31, 2012 Acquired above-market leases (included in identified intangible assets) [Member]	Dec. 31, 2012 Acquired in-place leases (included in other assets) [Member]	Dec. 31, 2012 Other Assets [Member]	Dec. 31, 2012 Acquired below-market leases (included in deferred revenue) [Member]	Jun. 07, 2013 Independence Plaza [Member]	Dec. 21, 2012 Independence Plaza [Member] Residential	Jun. 07, 2013 Independence Plaza [Member] Vornado Realty Trust [Member]	Jun. 07, 2013 Independence Plaza [Member] Five year interest only loan bearing interest rate of 3.48%
Business Acquisition [Line Items]
Variable Interest Entity Ownership Percentage												58.75%
Number of Units in Real Estate Property												1,328
Purchase Price Allocation, Land				$ 309,848
Purchase Price Allocation, Buildings						527,578
Purchase Price Allocation, Assets Acquired		844,800	602,662		252,844		13,115	67,879	7,374	(99,074)
Debt Instruments [Abstract]
Mortgages payable	8,582,573	8,663,326									323,000			550,000
Debt Term														5 years
Interest Rate, End of Period														3.48%
Net proceeds after repaying the existing loan and closing costs											219,000		137,000
Equity Method Investment, Ownership Percentage Sold											8.65%
Sale of economic interest, value											$ 41,000
Vornado's economic interest in subsidiary after sale											50.10%