Quarterly report pursuant to Section 13 or 15(d)

SUBSEQUENT EVENTS (Details)

v3.4.0.3
SUBSEQUENT EVENTS (Details)
1 Months Ended 3 Months Ended
May. 06, 2016
USD ($)
component
Aug. 13, 2015
USD ($)
component
May. 10, 2016
USD ($)
property
shares
Mar. 31, 2016
USD ($)
property
Mar. 31, 2015
USD ($)
property
Dec. 31, 2015
USD ($)
Apr. 01, 2014
USD ($)
Subsequent Event [Line Items]              
Number of self storage properties acquired | property       17 6    
Cash consideration for acquired self storage properties       $ 62,669,000 $ 6,991,000    
Consideration given, value of OP Equity       19,068,000      
Debt outstanding       634,312,000   $ 567,795,000  
Credit Facility [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Increase in credit facility   $ 125,000,000.0          
Current borrowing capacity   $ 550,000,000.0          
Number of lender agreement components | component   2          
Credit Facility [Member] | Revolving line of credit [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Maximum borrowing capacity       $ 90,525,000.000     $ 350,000,000.0
Revolver extension fee, percent       0.20%      
LIBOR [Member] | Credit Facility [Member] | Revolving line of credit [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Borrowing rate spread       1.60%      
Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property     22        
Aggregate purchase price of self storage properties acquired subsequent to period end     $ 173,800,000        
Cash consideration for acquired self storage properties     43,300,000        
Debt assumed in connection with self storage property acquisition     6,300,000        
Consideration given, value of OP Equity     79,900,000        
Other working capital liabilities assumed     $ 1,100,000        
Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member] | HIde-Away [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property     14        
Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member] | Participating Regional Operator [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property     15        
Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member] | Unidentified Third Parties [Member]              
Subsequent Event [Line Items]              
Number of self storage properties acquired | property     7        
Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member] | Mortgages [Member]              
Subsequent Event [Line Items]              
Debt assumed in connection with self storage property acquisition     $ 49,500,000        
Subsequent Event [Member] | Credit Facility [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Increase in credit facility $ 125,000,000.0            
Current borrowing capacity $ 675,000,000.0            
Number of lender agreement components | component 3            
Debt instrument, covenant compliance, maximum leverage ratio 60.00%            
Debt instrument, covenant compliance, minimum interest coverage ratio 1.5            
Debt instrument, covenant compliance, required minimum net worth $ 682,600,000.0            
Debt instrument, covenant compliance, required minimum net worth, addition to base, percent of equity issuances 75.00%            
Debt instrument, covenant compliance, maximum unsecured debt to unencumbered asset ratio 60.00%            
Debt instrument, covenant compliance, unencumbered net operating income to unsecured interest expense ratio 2.0            
Subsequent Event [Member] | Credit Facility [Member] | Revolving line of credit [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Maximum borrowing capacity $ 350,000,000            
Revolver maturity period 4 years            
Revolver, extension maturity period 5 years            
Revolver extension fee, percent 0.15%            
Debt outstanding $ 181,500,000            
Remaining borrowing capacity 168,500,000            
Subsequent Event [Member] | Credit Facility [Member] | Tranche A Term Loan [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Maximum borrowing capacity $ 225,000,000            
Revolver maturity period 5 years            
Debt outstanding $ 225,000,000            
Subsequent Event [Member] | Credit Facility [Member] | Tranche B Term Loan [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Maximum borrowing capacity $ 100,000,000            
Revolver maturity period 6 years            
Debt outstanding $ 100,000,000            
Subsequent Event [Member] | Prime Rate [Member] | Credit Facility [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Borrowing rate spread 0.50%            
Subsequent Event [Member] | LIBOR [Member] | Credit Facility [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Borrowing rate spread 1.00%            
Minimum [Member] | Subsequent Event [Member] | Credit Facility [Member] | Revolving line of credit [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Elective unused borrowing capacity fee 0.15%            
Unused borrowing capacity fee $ 0.00125            
Minimum [Member] | Subsequent Event [Member] | LIBOR [Member] | Credit Facility [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Leverage based margin threshold 1.35%            
Elective leverage based margin threshold 0.85%            
Minimum [Member] | Subsequent Event [Member] | Base Rate [Member] | Credit Facility [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Leverage based margin threshold 0.35%            
Elective leverage based margin threshold 0.00%            
Maximum [Member] | Subsequent Event [Member] | Credit Facility [Member] | Revolving line of credit [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Elective unused borrowing capacity fee 0.25%            
Unused borrowing capacity fee $ 0.003            
Maximum [Member] | Subsequent Event [Member] | LIBOR [Member] | Credit Facility [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Leverage based margin threshold 2.15%            
Elective leverage based margin threshold 2.30%            
Maximum [Member] | Subsequent Event [Member] | Base Rate [Member] | Credit Facility [Member] | Line of Credit [Member]              
Subsequent Event [Line Items]              
Leverage based margin threshold 1.15%            
Elective leverage based margin threshold 1.30%            
OP units [Member] | Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member]              
Subsequent Event [Line Items]              
Number of units issued for acquisitions | shares     2,348,464        
Subordinated performance units [Member] | Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member]              
Subsequent Event [Line Items]              
Number of units issued for acquisitions | shares     1,467,386        
Due Diligence Costs [Member] | Management [Member] | Subsequent Event [Member] | Participating Regional Operator [Member]              
Subsequent Event [Line Items]              
Due diligence expenses payable to the PROs     $ 100,000