ACQUISITION AND DISPOSITION OF PROPERTIES AND DISCONTINUED OPERATIONS Acquisitions (Details) (USD $) Share data in Millions, unless otherwise specified					12 Months Ended									1 Months Ended		12 Months Ended
	Dec. 31, 2013 Acquisitions in 2013 [Member] Preliminary Purchase Price Allocation [Member]	Dec. 31, 2012 Acquisitions in 2012 [Member] Preliminary Purchase Price Allocation [Member]	Dec. 31, 2013 Acquisitions in 2012 [Member] Finalized Purchase Price Allocation, Adjustment [Member]	Dec. 31, 2013 Acquisitions in 2012 [Member] Finalized Purchase Price Allocation [Member]	Dec. 31, 2013 Core Portfolio [Member] sqft	Dec. 31, 2013 Core Portfolio [Member] 664 North Michigan Avenue [Member] Chicago, Illinois [Member] sqft	Dec. 31, 2013 Core Portfolio [Member] 8-12 East Walton [Member] Chicago, Illinois [Member] sqft	Dec. 31, 2013 Core Portfolio [Member] 3200 - 3204 M Street [Member] Washington, D.C. [Member] sqft	Dec. 31, 2013 Core Portfolio [Member] 868 Broadway [Member] New York New York [Member] sqft	Dec. 31, 2013 Core Portfolio [Member] 313 - 315 Bowery [Member] New York New York [Member] sqft	Dec. 31, 2013 Core Portfolio [Member] 120 West Broadway [Member] New York New York [Member] sqft		Dec. 31, 2013 Fund III [Member]	May 31, 2012 Fund III [Member] Brooklyn, New York [Member] sqft	Apr. 30, 2012 Fund III [Member] Brooklyn, New York [Member]	Dec. 31, 2013 Fund IV [Member] sqft	Dec. 31, 2013 Fund IV [Member] AMCB Kennedy LLC [Member] North Bergen, New Jersey [Member] sqft		Dec. 31, 2013 Fund IV [Member] Promenade at Manassas [Member] Manassas, Virginia [Member] sqft		Dec. 31, 2013 Fund IV [Member] Paramus Plaza [Member] Paramus, New Jersey [Member] sqft	Dec. 31, 2013 Fund IV [Member] 1151 Third Avenue [Member] New York New York [Member] sqft	Dec. 31, 2013 Fund IV [Member] Lake Montclair [Member] Dumfries, Virginia [Member] sqft	Dec. 31, 2013 Fund IV [Member] 938 West North Avenue [Member] Chicago, Illinois [Member] sqft	Dec. 31, 2013 Fund II [Member] sqft
Business Acquisition [Line Items]
GLA (in square feet)					56,004	18,141	8,244	7,000	2,031	6,600	13,988	[1]				624,378	53,680	[2]	265,442	[2]	152,118	12,288	105,850	35,000	981,800
Percent Owned						100.00%	100.00%	100.00%	100.00%	100.00%	100.00%	[1]		99.00%			90.00%	[2]	90.00%	[2]	50.00%	100.00%	100.00%	80.00%
Purchase Price					$ 176,900,000	$ 86,600,000	$ 22,500,000	$ 11,800,000	$ 13,500,000	$ 5,500,000	$ 37,000,000	[1]				$ 123,200,000	$ 9,000,000	[2]	$ 38,000,000	[2]	$ 18,900,000	$ 18,000,000	$ 19,300,000	$ 20,000,000
Liabilities Incurred															23,000,000
Issuance of OP Units in Exchange for Ownership, Number of Shares											1.2
Acquisition Related Costs					2,700,000								800,000			2,000,000
Note receivable, discounted price															18,500,000
Property pledged as collateral, area of property														79,526
Business acquisition, percentage of voting interests acquired, counterparty interest														1.00%
Business Acquisition, Purchase Price Allocation [Abstract]
Land	65,829,000	86,826,000	30,312,000	117,138,000
Buildings and Improvements	253,724,000	226,650,000	(32,440,000)	194,210,000
Acquisition-related intangible assets (in Acquired lease intangibles, net)		0	31,965,000	31,965,000
Acquisition-related intangible liabilities (in Acquired lease intangibles, net)		0	(27,592,000)	(27,592,000)
Above-below market debt assumed (included in Mortgages and other notes payable)		0	(2,245,000)	(2,245,000)
Total Consideration	$ 319,553,000	$ 313,476,000	$ 0	$ 313,476,000

[1] This acquisition was primarily funded with the issuance of 1.2 million OP Units.

[2] As the joint venture partners to these investments maintain operating control over the investments, these are accounted for under the equity method.