SEGMENT INFORMATION - Revenue and Net Real Estate Property (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenues:
Revenues	$ 976,078	$ 918,940	$ 2,805,563	$ 2,874,192
Net real estate property:
Total net real estate property	21,791,995		21,791,995		$ 20,550,035
United States
Revenues:
Revenues	859,524	817,949	2,460,534	2,569,467
Net real estate property:
Total net real estate property	18,545,381		18,545,381		17,303,816
Canada
Revenues:
Revenues	109,046	96,896	322,422	287,056
Net real estate property:
Total net real estate property	2,997,492		2,997,492		2,983,924
United Kingdom
Revenues:
Revenues	7,508	$ 4,095	22,607	$ 17,669
Net real estate property:
Total net real estate property	$ 249,122		$ 249,122		$ 262,295