SEGMENT INFORMATION - Revenue and Net Real Estate Property (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenues:
Total revenues	$ 1,012,054	$ 942,874
Net real estate property:
Total net real estate property	20,967,276		$ 21,729,087
United States
Revenues:
Total revenues	908,193	888,281
Net real estate property:
Total net real estate property	18,089,200		18,631,352
Canada
Revenues:
Total revenues	96,970	47,597
Net real estate property:
Total net real estate property	2,631,249		2,830,850
United Kingdom
Revenues:
Total revenues	6,891	$ 6,996
Net real estate property:
Total net real estate property	$ 246,827		$ 266,885