Quarterly report pursuant to Section 13 or 15(d)

SUBSEQUENT EVENTS (Details)

v3.8.0.1
SUBSEQUENT EVENTS (Details)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended 9 Months Ended
Oct. 11, 2017
USD ($)
$ / shares
shares
Nov. 07, 2017
USD ($)
property
shares
Sep. 30, 2017
USD ($)
property
Jun. 30, 2017
USD ($)
property
Mar. 31, 2017
USD ($)
property
Sep. 30, 2017
USD ($)
property
Sep. 30, 2016
USD ($)
Subsequent Event [Line Items]              
Number of self storage properties acquired | property     19 10 5 34  
Consideration given, value of OP Equity     $ 267 $ 8,931 $ 4,964 $ 14,162  
Contributions to unconsolidated real estate venture           12,647 $ 4,873
Equity Method Investee [Member] | Real Estate Venture [Member]              
Subsequent Event [Line Items]              
Estimated fair value of self storage properties acquired by unconsolidated real estate venture           49,800  
Contributions to unconsolidated real estate venture           $ 12,500  
Subsequent Event [Member] | Redeemable Preferred Shares [Member]              
Subsequent Event [Line Items]              
Public offering of preferred shares | shares 6,900,000            
Preferred shares, dividend rate (percent) 6.00%            
Preferred shares issued upon exercise of underwriter options | shares 900,000            
Proceeds from issuance of preferred shares $ 166,600            
Preferred stock, redemption price (in dollars per share) | $ / shares $ 25.00            
Subsequent Event [Member] | Self Storage Properties [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property   28          
Aggregate purchase price of properties acquired   $ 174,500          
Cash payments to acquire properties, net of cash received   165,000          
Consideration given, value of OP Equity   7,400          
Acquisition of properties, liabilities assumed   $ 2,100          
Subsequent Event [Member] | Self Storage Properties [Member] | OP units [Member]              
Subsequent Event [Line Items]              
Consideration, equity interest issued (in shares) | shares   260,490          
Subsequent Event [Member] | Self Storage Properties [Member] | Subordinated performance units [Member]              
Subsequent Event [Line Items]              
Consideration, equity interest issued (in shares) | shares   45,335          
Subsequent Event [Member] | Affiliated Entity [Member]              
Subsequent Event [Line Items]              
Proceeds from issuance of subordinated performance units   $ 1,100          
Subsequent Event [Member] | Equity Method Investee [Member] | Real Estate Venture [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property   1          
Estimated fair value of self storage properties acquired by unconsolidated real estate venture   $ 9,300          
Contributions to unconsolidated real estate venture   $ 2,400          
Subsequent Event [Member] | Acquisition of Self Storage Property Nordhagen LLLP [Member] | Affiliated Entity [Member] | Self Storage Properties [Member] | OP units [Member]              
Subsequent Event [Line Items]              
Consideration, equity interest issued (in shares) | shares   26,049          
Subsequent Event [Member] | Acquisition of Self Storage Property SecurCare SelfStorage Inc [Member] | Affiliated Entity [Member] | Self Storage Properties [Member] | Subordinated performance units [Member]              
Subsequent Event [Line Items]              
Consideration, equity interest issued (in shares) | shares   22,214          
Subsequent Event [Member] | Due Diligence Costs [Member] | Management [Member]              
Subsequent Event [Line Items]              
Due diligence expenses payable to the PROs   $ 300