INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Condensed Financial Position (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
ASSETS
Self storage properties	$ 5,818,388		$ 5,792,174
Less accumulated depreciation	(961,977)		(874,359)
Self storage properties, net	4,856,411		4,917,815
Other assets	138,522		134,002
Total assets	5,321,101		5,931,811
LIABILITIES AND EQUITY
Debt financing	3,365,836		3,658,205
Equity	1,817,065	$ 1,947,072	2,125,841	$ 2,384,401	$ 2,405,074	$ 2,389,014
Total liabilities and equity	5,321,101		5,931,811
Joint venture | Unconsolidated real estate ventures
ASSETS
Self storage properties	2,547,923		2,200,522
Less accumulated depreciation	(405,518)		(369,412)
Self storage properties, net	2,142,405		1,831,110
Other assets	45,696		37,826
Total assets	2,188,101		1,868,936
LIABILITIES AND EQUITY
Debt financing	1,212,592		1,003,223
Other liabilities	34,110		28,333
Equity	941,399		837,380
Total liabilities and equity	$ 2,188,101		$ 1,868,936