REAL ESTATE AND ACCUMULATED DEPRECIATION (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Estimated useful lives
Aggregate cost of total real estate for federal income tax purposes	$ 22,635,619
Changes in total real estate assets
Balance, beginning of period	22,342,576	$ 21,935,936	$ 20,776,626
Acquisitions, construction costs and improvements	1,615,949	1,568,878	1,526,516
Dispositions, including impairment loss on planned dispositions	(351,653)	(1,162,238)	(367,206)
Balance, end of period	23,606,872	22,342,576	21,935,936
Changes in accumulated depreciation
Balance, beginning of period	4,611,646	4,218,379	3,743,632
Depreciation, including discontinued operations	661,578	631,196	584,150
Dispositions	(99,341)	(237,929)	(109,403)
Balance, end of period	$ 5,173,883	$ 4,611,646	$ 4,218,379
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