SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues and net operating income for each of the reportable segments
Total revenues	$ 166,813	$ 161,765	$ 500,548	$ 469,276
Net operating income, including reconciling items	107,958	104,039	320,250	297,033
General and administrative expenses	(6,152)	(8,018)	(22,572)	(27,367)
Interest expense	(28,161)	(31,874)	(88,048)	(92,766)
Depreciation and amortization	(44,005)	(41,720)	(129,860)	(120,234)
Other expenses	(16)	(15)	(48)	(2,726)
Income from continuing operations	29,624	22,412	79,722	53,940
Operating segment | Core properties
Revenues and net operating income for each of the reportable segments
Threshold period of time owned	1 year
Total revenues	154,221	150,309	463,793	448,816
Net operating income, including reconciling items	99,643	96,507	296,153	283,894
Operating segment | Non-core properties
Revenues and net operating income for each of the reportable segments
Total revenues	12,385	11,424	36,084	20,397
Net operating income, including reconciling items	8,108	7,500	23,426	13,076
Reconciling items
Revenues and net operating income for each of the reportable segments
Total revenues	207	32	671	63
Net operating income, including reconciling items	$ 207	$ 32	$ 671	$ 63