SELF STORAGE PROPERTIES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Real Estate [Abstract]
Land	$ 680,035		$ 649,938
Buildings and improvements	2,627,812		2,435,171
Furniture and equipment	7,002		6,610
Total self storage properties	3,314,849		3,091,719
Less accumulated depreciation	(363,527)		(337,822)
Self storage properties, net	2,951,322		$ 2,753,897
Depreciation expense related to self storage properties	$ 25,700	$ 21,500