ACQUISITION AND DISPOSITION OF REAL ESTATE AND DISCONTINUED OPERATIONS Acquisitions (Details) (USD $)	9 Months Ended				1 Months Ended					1 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Core Portfolio	Sep. 30, 2013 Fund IV	Apr. 30, 2012 Brooklyn, New York Fund III sqft	Mar. 31, 2013 664 North Michigan Avenue [Member] Chicago Illinois Core Portfolio sqft	Jun. 30, 2013 Eight-Twelve East Walton Chicago Illinois Core Portfolio sqft	Jun. 30, 2013 3200 -3204 M Street Washington, D.C. Core Portfolio sqft	Feb. 28, 2013 Shopping Center Brooklyn, New York Fund III	Aug. 31, 2013 Twenty Eight Nineteen Kennedy Boulevard North Bergen, New Jersey Fund IV sqft	Jun. 30, 2013 Twenty Eight Nineteen Kennedy Boulevard North Bergen, New Jersey Fund IV sqft	Jun. 30, 2013 Promenade at Manassas Manassas, Virginia Fund IV sqft	Sep. 30, 2013 Acquisitions in 2013 Preliminary Purchase Price Allocation	Dec. 31, 2012 Acquisitions in 2012 Preliminary Purchase Price Allocation	Sep. 30, 2013 Acquisitions in 2012 Scenario, Adjustment	Sep. 30, 2013 Acquisitions in 2012 Finalized Purchase Price Allocation
Business Acquisition [Line Items]
Square Footage of Real Estate Property (in square feet)					79,526	18,141	8,244	7,000		152,118	53,680	265,442
Business Acquisition, Cost of Acquired Entity, Purchase Price						$ 86,600,000	$ 22,500,000	$ 11,800,000		$ 18,900,000	$ 9,000,000	$ 38,000,000
Business Combination, Acquisition Related Costs			1,600,000	1,800,000
Payments to Acquire Notes Receivable	0	34,500,000			18,500,000
Debt instrument face amount					23,000,000
Consolidated Joint Venture, Ownership Percentage									99.00%	50.00%	98.00%	99.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners									1.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net
Land													47,242,000	38,028,000	2,819,000	40,847,000
Buildings and improvements													159,045,000	80,997,000	(1,971,000)	79,026,000
Acquisition-related intangible assets (in Acquired lease intangibles, net)														0	11,069,000	11,069,000
Acquisition-related intangible liabilities (in Acquired lease intangibles, net)														0	(9,672,000)	(9,672,000)
Below market debt assumed (in Mortgage and other notes payable)														0	(2,245,000)	(2,245,000)
Total consideration													$ 206,287,000	$ 119,025,000	$ 0	$ 119,025,000