SEGMENT INFORMATION - Revenue and Net Real Estate Property (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Revenues:
Total revenues	$ 918,940	$ 983,155	$ 2,874,192	$ 2,876,746
Net real estate property:
Total net real estate property	20,978,412		20,978,412		$ 21,734,573
United States
Revenues:
Total revenues	817,949	904,031	2,569,467	2,688,329
Net real estate property:
Total net real estate property	17,874,378		17,874,378		18,636,839
Canada
Revenues:
Total revenues	96,896	72,495	287,056	167,881
Net real estate property:
Total net real estate property	2,853,245		2,853,245		2,830,850
United Kingdom
Revenues:
Total revenues	4,095	$ 6,629	17,669	$ 20,536
Net real estate property:
Total net real estate property	$ 250,789		$ 250,789		$ 266,885