SEGMENT INFORMATION - Revenue and Net Real Estate Property (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Revenues:
Total revenues	$ 983,155	$ 936,538	$ 2,876,746	$ 2,822,547
Net real estate property:
Total net real estate property	21,932,038		21,932,038		$ 20,093,657
United States
Revenues:
Total revenues	904,031	881,477	2,688,329	2,656,487
Net real estate property:
Total net real estate property	18,917,383		18,917,383		18,861,163
Canada
Revenues:
Total revenues	72,495	48,080	167,881	144,366
Net real estate property:
Total net real estate property	2,764,468		2,764,468		963,588
United Kingdom
Revenues:
Total revenues	6,629	$ 6,981	20,536	$ 21,694
Net real estate property:
Total net real estate property	$ 250,187		$ 250,187		$ 268,906