Acquisitions (Details) (USD $)	9 Months Ended			0 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Jul. 05, 2012 Fifth Avenue 666 [Member]	Jul. 05, 2012 Fifth Avenue 666 [Member] Retail Units [Member] ft sqft	Jul. 05, 2012 Fifth Avenue 666 [Member] Retail Units [Member] Fee Simple [Member] sqft	Jul. 05, 2012 Fifth Avenue 666 [Member] Retail Units [Member] Leasehold Interest [Member] sqft	Jul. 30, 2012 Marriott Marquis Time Square Hotel [Member] Hotel [Member] sqft	Jul. 30, 2012 Marriott Marquis Time Square Hotel [Member] Hotel [Member] Minimum [Member] Rooms
Acquisitions [Line Items]
Business Acquisition, Description of Acquired Entity				we entered into an agreement to acquire a retail condominium located at 666 Fifth Avenue at 53rd Street for $707,000,000. The property has 126 feet of frontage on Fifth Avenue and contains 114,000 square feet, 39,000 square feet in fee and 75,000 square feet by long-term lease from the 666 Fifth Avenue office condominium, which is 49.5% owned by Vornado			we entered into a lease with Host Hotels & Resorts, Inc. (NYSE: HST) (“Host”), under which we will redevelop the retail and signage components of the Marriott Marquis Times Square Hotel. The Marriott Marquis with over 1,900 rooms is one of the largest hotels in Manhattan. It is located in the heart of the bow-tie of Times Square and spans the entire block front from 45th Street to 46th Street on Broadway.
Square Footage Of Real Estate Property				114,000	39,000	75,000
Number of Units in Real Estate Property								1,900
Business Acquisition Cost Of Acquired Entity Purchase Price				$ 707,000,000
Equity method ownership percentage			49.50%
Redevelopment Expenditures Planned							140,000,000
Length of storefront in feet				126			300
Marriott Marquis Times Square Hotel - retail and signage capital lease: Asset (included in development costs and construction in progress)	240,000,000	0					240,000,000
Marriott Marquis Times Square Hotel - retail and signage capital lease: Liability (included in other liabilities)	(240,000,000)	0					(240,000,000)
Capital Leases, Future Minimum Payments Due, Current							$ 12,500,000
Preferred Return Percentage							5.20%