REAL ESTATE AND ACCUMULATED DEPRECIATION (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Estimated useful lives
Aggregate cost of total real estate for federal income tax purposes	$ 20,223
Changes in total real estate assets
Balance, beginning of period	19,268,099	$ 17,849,316	$ 16,800,321
Acquisitions, construction costs and improvements	1,788,515	1,667,989	1,311,003
Dispositions, including impairment loss on planned dispositions	(279,988)	(249,206)	(262,008)
Balance, end of period	20,776,626	19,268,099	17,849,316
Changes in accumulated depreciation
Balance, beginning of period	3,325,790	2,913,576	2,516,112
Depreciation, including discontinued operations	531,434	477,923	442,682
Dispositions	(113,592)	(65,709)	(45,218)
Balance, end of period	$ 3,743,632	$ 3,325,790	$ 2,913,576
Building
Estimated useful lives
Estimated useful lives of assets (in years)	30 years
Improvements, upgrades and FF&E
Estimated useful lives
Estimated useful lives of assets (in years)	7 years