Quarterly report pursuant to Section 13 or 15(d)

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURE - Narrative (Details)

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INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURE - Narrative (Details)
storage_unit in Thousands, $ in Thousands, ft² in Millions
6 Months Ended
Jun. 30, 2018
USD ($)
ft²
storage_unit
state
property
Jun. 30, 2017
USD ($)
Dec. 31, 2016
property
Schedule of Equity Method Investments [Line Items]      
Number of self storage properties | property 551    
Total rentable square feet in self storage properties owned by the Joint Venture | ft² 34.0    
Number of storage units owned by the Joint Venture | storage_unit 270    
Number of states that the Joint Venture self storage properties are owned in | state 29    
Contributions to the Joint Venture | $ $ 2,390 $ 12,647  
Joint Venture | Unconsolidated real estate venture      
Schedule of Equity Method Investments [Line Items]      
Number of self storage properties | property     66
Number of self storage properties acquired by the Joint Venture | property 1    
Aggregate purchase price of properties acquired by the Joint Venture | $ $ 9,500    
Contributions to the Joint Venture | $ $ 2,400    
Company's proportionate share of its Joint Venture (percent) 25.00%