Annual report pursuant to Section 13 and 15(d)

ORGANIZATION AND NATURE OF OPERATIONS - Narrative (Details)

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ORGANIZATION AND NATURE OF OPERATIONS - Narrative (Details)
ft² in Millions
Dec. 31, 2018
ft²
storage_unit
state
property
Schedule of Equity Method Investments [Line Items]  
Number of self storage properties | property 675
Number of states that self storage properties are in | state 34
Total rentable square feet in self storage properties | ft² 43.0
Number of storage units | storage_unit 345,000
Consolidated Properties [Member]  
Schedule of Equity Method Investments [Line Items]  
Number of self storage properties | property 499
Number of states that self storage properties are in | state 26
Total rentable square feet in self storage properties | ft² 30.4
Number of storage units | storage_unit 242,000
Unconsolidated Properties [Member] | Unconsolidated Real Estate Venture [Member] | Corporate Joint Venture [Member]  
Schedule of Equity Method Investments [Line Items]  
Number of self storage properties | property 176
Number of states that self storage properties are in | state 22
Total rentable square feet in self storage properties | ft² 12.6
Number of storage units | storage_unit 103,000