SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2025 USD ($) property partnership	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) property partnership	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Variable Interest Entity [Line Items]
Total shareholders' equity	$ 973,125,000		$ 973,125,000		$ 1,075,980,000
Additional paid-in capital	1,252,488,000		1,252,488,000		1,249,426,000
Accumulated other comprehensive income	4,860,000		4,860,000		15,548,000
Noncontrolling interests	$ 608,916,000		$ 608,916,000		687,367,000
Number of self storage properties | property	1,069		1,069
Self storage properties, net	$ 4,666,096,000		$ 4,666,096,000		4,812,496,000
Principal amount	3,413,567,000		$ 3,413,567,000		3,459,093,000
Property management fees as percent of monthly gross revenues and net sales revenue of unconsolidated real estate venture assets			4.00%
Tenant Insurance and Tenant Warranty Protection Plan Revenues
Variable Interest Entity [Line Items]
Revenue	5,700,000	$ 6,300,000	$ 17,500,000	$ 17,100,000
Retail Products and Supplies
Variable Interest Entity [Line Items]
Revenue	400,000	500,000	1,200,000	1,500,000
Property Management, Call Center, and Platform Fees
Variable Interest Entity [Line Items]
Revenue	4,700,000	4,700,000	$ 14,100,000	13,500,000
Property management fees as percent of monthly gross revenues and net sales revenue of unconsolidated real estate venture assets			6.00%
Platform fees per unconsolidated real estate venture property per month			$ 1,250
Call center fees as percent of monthly gross revenues and net sales revenue of unconsolidated real estate venture assets			1.00%
Acquisition Fees
Variable Interest Entity [Line Items]
Revenue	200,000	600,000	$ 300,000	600,000
Tenant Warranty Protection or Tenant Insurance
Variable Interest Entity [Line Items]
Revenue	7,000,000.0	$ 6,100,000	$ 21,300,000	$ 15,600,000
Percent of total warranty protection plan proceeds received per unconsolidated real estate venture property			50.00%
Fixed rate mortgages payable | Mortgages
Variable Interest Entity [Line Items]
Principal amount	$ 199,167,000		$ 199,167,000		200,793,000
VIE, Primary Beneficiary
Variable Interest Entity [Line Items]
Number of partnerships considered to be VIEs | partnership	22		22
Number of self storage properties | property	49		49
Self storage properties, net	$ 398,500,000		$ 398,500,000		407,100,000
VIE, Primary Beneficiary | Fixed rate mortgages payable | Mortgages
Variable Interest Entity [Line Items]
Principal amount	172,900,000		172,900,000		$ 172,900,000
Revision of Prior Period, Error Correction, Adjustment
Variable Interest Entity [Line Items]
Total shareholders' equity	112,100,000		112,100,000
Additional paid-in capital	125,600,000		125,600,000
Accumulated other comprehensive income	13,500,000		13,500,000
Noncontrolling interests	$ 112,100,000		$ 112,100,000