SEGMENT INFORMATION - Revenue and Net Real Estate Property (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Revenues:
Revenues	$ 919,194	$ 943,198	$ 1,829,485	$ 1,955,252
Net real estate property:
Total net real estate property	20,130,030		20,130,030		$ 20,550,035
United States
Revenues:
Revenues	803,242	843,324	1,601,010	1,751,518
Net real estate property:
Total net real estate property	16,800,959		16,800,959		17,303,816
Canada
Revenues:
Revenues	108,342	93,190	213,375	190,160
Net real estate property:
Total net real estate property	3,070,191		3,070,191		2,983,924
United Kingdom
Revenues:
Revenues	7,610	$ 6,684	15,100	$ 13,574
Net real estate property:
Total net real estate property	$ 258,880		$ 258,880		$ 262,295