REAL ESTATE AND ACCUMULATED DEPRECIATION (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Estimated useful lives
Aggregate cost of total real estate for federal income tax purposes	$ 17,561,706
Changes in total real estate assets
Balance, beginning of period	16,800,321	10,071,342	9,288,496
Acquisitions, construction costs and improvements	1,311,003	7,157,639	934,935
Dispositions, including impairment loss on planned dispositions	(262,008)	(428,660)	(152,089)
Balance, end of period	17,849,316	16,800,321	10,071,342
Changes in accumulated depreciation
Balance, beginning of period	2,516,112	2,056,222	1,863,466
Depreciation, including discontinued operations	442,682	573,715	260,094
Dispositions	(45,218)	(113,825)	(67,338)
Balance, end of period	$ 2,913,576	$ 2,516,112	$ 2,056,222
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