Annual report pursuant to Section 13 and 15(d)

SUBSEQUENT EVENTS - Self Storage Property Acquisitions (Details)

v3.8.0.1
SUBSEQUENT EVENTS - Self Storage Property Acquisitions (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 2 Months Ended 12 Months Ended
Oct. 04, 2016
USD ($)
Jan. 31, 2018
USD ($)
property
Feb. 27, 2018
USD ($)
property
$ / shares
shares
Dec. 31, 2017
USD ($)
property
Dec. 31, 2016
USD ($)
property
Dec. 31, 2015
USD ($)
Dec. 31, 2014
property
Subsequent Event [Line Items]              
Contributions to unconsolidated real estate venture       $ 15,289 $ 82,950 $ 0  
Participating Regional Operator [Member] | Affiliated Entity [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property       10 23    
Participating Regional Operator [Member] | Management [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property             16
Participating Regional Operator [Member] | Due Diligence Costs [Member] | Management [Member]              
Subsequent Event [Line Items]              
Due diligence expenses payable to the PROs       $ 700 $ 1,100 $ 600  
Acquisition of Self Storage Properties [Member]              
Subsequent Event [Line Items]              
Aggregate purchase price $ 20,000            
Subsequent Event [Member] | Series A-1 Preferred Units [Member]              
Subsequent Event [Line Items]              
Preferred units redemption price (in dollars per share) | $ / shares     $ 25.00        
Preferred shares dividend rate (percent)     6.00%        
Subsequent Event [Member] | Affiliated Entity [Member]              
Subsequent Event [Line Items]              
Proceeds from issuance of subordinated equity     $ 2,100        
Subsequent Event [Member] | Equity Method Investee [Member] | Unconsolidated Real Estate Venture [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property   1          
Estimated fair value of self storage properties acquired   $ 9,300          
Contributions to unconsolidated real estate venture   $ 2,400          
Subsequent Event [Member] | Participating Regional Operator [Member] | Due Diligence Costs [Member] | Management [Member]              
Subsequent Event [Line Items]              
Due diligence expenses payable to the PROs     $ 200        
Subsequent Event [Member] | Acquisition of Self Storage Properties [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property     18        
Aggregate purchase price     $ 101,800        
Consideration given, cash     78,900        
Assumed working capital liabilities     500        
Consideration given, value of OP Equity     $ 22,400        
Subsequent Event [Member] | Acquisition of Self Storage Properties [Member] | Series A-1 Preferred Units [Member]              
Subsequent Event [Line Items]              
Consideration, equity interest issued (in shares) | shares     316,103        
Subsequent Event [Member] | Acquisition of Self Storage Properties [Member] | OP Units [Member]              
Subsequent Event [Line Items]              
Consideration, equity interest issued (in shares) | shares     464,056        
Subsequent Event [Member] | Acquisition of Self Storage Properties [Member] | Subordinated performance units [Member]              
Subsequent Event [Line Items]              
Consideration, equity interest issued (in shares) | shares     56,228