REAL ESTATE AND ACCUMULATED DEPRECIATION (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Estimated useful lives
Aggregate cost of total real estate for federal income tax purposes	$ 21,480
Changes in total real estate assets
Balance, beginning of period	21,935,936	$ 20,776,626	$ 19,268,099
Acquisitions, construction costs and improvements	1,568,878	1,526,516	1,788,515
Dispositions, including impairment loss on planned dispositions	(1,162,238)	(367,206)	(279,988)
Balance, end of period	22,342,576	21,935,936	20,776,626
Changes in accumulated depreciation
Balance, beginning of period	4,218,379	3,743,632	3,325,790
Depreciation, including discontinued operations	631,196	584,150	531,434
Dispositions	(237,929)	(109,403)	(113,592)
Balance, end of period	$ 4,611,646	$ 4,218,379	$ 3,743,632
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