Aquisitions (Details) (USD $)	12 Months Ended				11 Months Ended			12 Months Ended		12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 06, 2012 Fifth Avenue 666 [Member]	Dec. 06, 2012 Fifth Avenue 666 [Member] Retail Units [Member] ft sqft	Dec. 06, 2012 Fifth Avenue 666 [Member] Retail Units [Member] Fee Simple [Member] sqft	Dec. 06, 2012 Fifth Avenue 666 [Member] Retail Units [Member] Leasehold Interest [Member] sqft	Dec. 31, 2012 Marriott Marquis Time Square Hotel [Member] Hotel [Member] ft	Jul. 30, 2012 Marriott Marquis Time Square Hotel [Member] Hotel [Member] Rooms	Dec. 21, 2012 Independance Plaza [Member]	Dec. 31, 2011 Independance Plaza [Member] sqft Residential	Dec. 31, 2012 Independance Plaza [Member]	Dec. 21, 2012 Independance Plaza [Member] Accelerated Amortization Of Discount On Subordinated Debt [Member]	Dec. 21, 2012 Independance Plaza [Member] Purchase Price Fair Value Adjustment [Member]	Dec. 31, 2011 Independance Plaza [Member] Warrant to purchase [Member]	Dec. 21, 2012 Independance Plaza [Member] Equity Partner Interest [Member]
Business Acquisition [Line Items]
Square Footage Of Real Estate Property					114,000	39,000	75,000				54,500
Number of Units in Real Estate Property									1,900		1,328
Business Acquisition Cost Of Acquired Entity Purchase Price						$ 707,000,000					$ 45,000,000				$ 1,000,000	$ 160,000,000
Percentage Of Equity Acquired By Warrant Purchase											25.00%
Equity method ownership percentage				49.50%							51.00%
Redevelopment Expenditures Planned								140,000,000
Length Of Storefront					126			300
Marriott Marquis Times Square - retail and signage capital lease: Asset (included in development costs and construction in progress)	249,285,000							240,000,000
Marriott Marquis Times Square Hotel - retail and signage capital lease: Liability (included in other liabilities)	(240,000,000)	0	0					(240,000,000)
Capital Leases Future Minimum Payments Due Current	12,500,000							12,500,000
Preferred Return Percentage								5.20%
Variable Interest Entity Ownership Percentage										58.75%
Variable Interest Entity, Initial Consolidation, Gain (Loss)										105,366,000			60,396,000	44,970,000
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets												844,800,000
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities												$ 334,225,000