SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Revenues and net operating income for each of the reportable segments
Total revenues	$ 176,644	$ 165,298
Net operating income, including reconciling items	109,337	99,727
General and administrative expenses	(8,543)	(9,258)
Interest expense	(25,485)	(24,852)
Depreciation and amortization	(47,864)	(43,778)
Other expenses	(377)	(8)
Impairment and other charges	(181)
Income from continuing operations, before gain on disposition of real estate	26,887	21,831
Operating Segments | Core Properties
Revenues and net operating income for each of the reportable segments
Threshold period of time owned	1 year
Total revenues	162,097	157,972
Net operating income, including reconciling items	100,356	95,435
Operating Segments | Non-core Properties
Revenues and net operating income for each of the reportable segments
Total revenues	11,800	3,678
Net operating income, including reconciling items	6,978	1,970
Operating Segments | Disposed properties
Revenues and net operating income for each of the reportable segments
Total revenues	2,430	3,507
Net operating income, including reconciling items	1,686	2,181
Reconciling Items
Revenues and net operating income for each of the reportable segments
Total revenues	317	141
Net operating income, including reconciling items	$ 317	$ 141