SEGMENT INFORMATION - Revenue and Net Real Estate Property (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenues:
Total revenues	$ 910,291	$ 1,012,054
Net real estate property:
Total net real estate property	20,321,761		$ 20,550,035
United States
Revenues:
Total revenues	797,768	908,193
Net real estate property:
Total net real estate property	17,032,537		17,303,816
Canada
Revenues:
Total revenues	105,033	96,970
Net real estate property:
Total net real estate property	3,028,035		2,983,924
United Kingdom
Revenues:
Total revenues	7,490	$ 6,891
Net real estate property:
Total net real estate property	$ 261,189		$ 262,295