ACQUISITION AND DISPOSITION OF REAL ESTATE AND PROPERTIES HELD FOR SALE - Dispositions & Properties Held For Sale (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016 USD ($) property	Dec. 31, 2015 property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties held for sale | property	1	0
Fund III | Cortlandt Town Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, percentage	65.00%
Sale Price	$ 107,250
Gain on Sale	$ 65,393