Subsequent Events (Narratives) (Details) (USD $)			0 Months Ended			0 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Aug. 05, 2014 Subsequent Event [Member] Senior Unsecured Notes Due 2039 [Member]	Jul. 16, 2014 Subsequent Event [Member] Las Catalinas Regional Mall [Member] sqft	Aug. 01, 2014 Subsequent Event [Member] Lexington Avenue 715 Retail [Member]	Jul. 23, 2014 Subsequent Event [Member] Sixty One Ninth Avenue Property [Member] sqft	Jul. 09, 2014 Subsequent Event [Member] Retail Condominium [Member] St. Regis Hotel [Member] ft	Jul. 09, 2014 Subsequent Event [Member] Maximum [Member] Retail Condominium [Member] St. Regis Hotel [Member]	Jul. 09, 2014 Subsequent Event [Member] Minimum [Member] Retail Condominium [Member] St. Regis Hotel [Member]
Subsequent Event [Line Items]
Cost of acquired entity purchase price					$ 63,000,000		$ 700,000,000
Frontage Length							100
Equity method ownership percentage								80.00%	67.00%
Mortgages payable (in US Dollars)	8,988,843,000	8,331,993,000		130,000,000
Square Footage Of Real Estate Property				494,000		130,000
Debt Term				10 years
Interest Rate, End of Period (in percentage)				4.43%
Debt Instrument Amortization Period				30 years
Debt Maturity Beginning Period				6 years
Lease Expiration Term						99 years
Joint Venture Partnership Percent						50.00%
Estimated Development Cost						125,000,000
Debt Instrument Redemption Amount			$ 445,000,000
Interest Rate, Stated			7.875%
Debt Instrument, Maturity Date			Oct. 01, 2039
Debt Instrument, Redemption Period, End Date			Oct. 01, 2014
Debt Instrument, Redemption Price, Percentage			100.00%