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)
$ in Thousands, ft² in Millions
6 Months Ended
Jun. 30, 2017
USD ($)
ft²
storage_unit
state
property
Jun. 30, 2016
USD ($)
Schedule of Equity Method Investments [Line Items]    
Number of self storage properties | property 394  
Total rentable square feet in self storage properties owned by the unconsolidated real estate venture | ft² 23.9  
Number of storage units owned by unconsolidated real estate venture | storage_unit 190,000  
Number of states that unconsolidated real estate venture self storage properties are owned in | state 21  
Contributions to unconsolidated real estate venture | $ $ 12,647 $ 0
Equity Method Investee [Member] | Real Estate Venture [Member]    
Schedule of Equity Method Investments [Line Items]    
Number of self storage properties | property 70  
Total rentable square feet in self storage properties owned by the unconsolidated real estate venture | ft² 4.9  
Number of storage units owned by unconsolidated real estate venture | storage_unit 39,000  
Number of states that unconsolidated real estate venture self storage properties are owned in | state 13  
Number of self storage properties acquired by unconsolidated venture | storage_unit 4  
Estimated fair value of self storage properties acquired by unconsolidated real estate venture | $ $ 49,800  
Contributions to unconsolidated real estate venture | $ $ 12,500  
Company's proportionate share of its unconsolidated real estate venture (percent) 25.00%