Annual report pursuant to Section 13 and 15(d)

SUBSEQUENT EVENTS (Details)

v3.6.0.2
SUBSEQUENT EVENTS (Details)
 2 Months Ended 12 Months Ended
Feb. 08, 2017
USD ($)
Oct. 04, 2016
USD ($)
Feb. 28, 2017
USD ($)
property
shares
Dec. 31, 2016
USD ($)
property
Dec. 31, 2015
USD ($)
property
Dec. 31, 2014
USD ($)
property
Subsequent Event [Line Items]            
Number of self storage properties acquired | property       107 58 83
Consideration given, cash       $ 532,529,000 $ 171,822,000 $ 217,939,000
Series of Individually Immaterial Business Acquisitions [Member]            
Subsequent Event [Line Items]            
Aggregate purchase price   $ 20,000,000        
Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member]            
Subsequent Event [Line Items]            
Number of self storage properties acquired | property     5      
Aggregate purchase price     $ 31,800,000      
Consideration given, cash     26,600,000      
Consideration given, value of vesting LTIP units     5,000,000      
Assumed working capital liabilities     $ 200,000      
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     2      
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     3      
Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member] | OP units [Member]            
Subsequent Event [Line Items]            
Units issued for acquisition | shares     174,694      
Subsequent Event [Member] | Series of Individually Immaterial Business Acquisitions [Member] | Subordinated performance units [Member]            
Subsequent Event [Line Items]            
Units issued for acquisition | shares     47,332      
Management [Member] | Participating Regional Operator [Member]            
Subsequent Event [Line Items]            
Number of self storage properties acquired | property           16
Management [Member] | Subsequent Event [Member] | Participating Regional Operator [Member]            
Subsequent Event [Line Items]            
Partners' Capital Account, Contributions     $ 7,000,000      
Due Diligence Costs [Member] | Management [Member] | Subsequent Event [Member] | Participating Regional Operator [Member]            
Subsequent Event [Line Items]            
Fees and expenses     $ 100,000      
Amended Credit Facility [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Increase in total borrowing capacity $ 170,000,000.0          
Maximum borrowing capacity 895,000,000          
Amended Credit Facility [Member] | Tranche A Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Line of Credit Facility, Maximum Borrowing Capacity Increase 10,000,000          
Maximum borrowing capacity 235,000,000          
Amended Credit Facility [Member] | Tranche B Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Line of Credit Facility, Maximum Borrowing Capacity Increase 55,000,000          
Maximum borrowing capacity 155,000,000          
Amended Credit Facility [Member] | Tranche C Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Maximum borrowing capacity $ 105,000,000          
Prepayment premiums rate, Increase Agreement through first anniversary 2.00%          
Prepayment premiums rate, first anniversary through Increase Agreement 1.00%          
Amended Credit Facility [Member] | Tranche C Term Loan [Member] | Subsequent Event [Member] | Line of Credit [Member]            
Subsequent Event [Line Items]            
Maximum borrowing capacity $ 105,000,000.0          
Amended Credit Facility [Member] | Revolving line of credit [Member] | Subsequent Event [Member] | Line of Credit [Member]            
Subsequent Event [Line Items]            
Maximum borrowing capacity 400,000,000          
Expansion Option Of Amended Credit Facility [Member] | Subsequent Event [Member] | Line of Credit [Member]            
Subsequent Event [Line Items]            
Maximum borrowing capacity $ 1,000,000,000.0          
Federal Funds Effective Swap Rate [Member] | Amended Credit Facility [Member] | Tranche C Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Borrowing rate spread 0.50%          
London Interbank Offered Rate (LIBOR) [Member] | Amended Credit Facility [Member] | Tranche C Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Borrowing rate spread 1.00%          
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Amended Credit Facility [Member] | Tranche C Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Leverage based margin threshold 1.70%          
Elective leverage based margin threshold 1.50%          
Minimum [Member] | Base Rate [Member] | Amended Credit Facility [Member] | Tranche C Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Leverage based margin threshold 0.70%          
Elective leverage based margin threshold 0.50%          
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Amended Credit Facility [Member] | Tranche C Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Leverage based margin threshold 2.25%          
Elective leverage based margin threshold 2.45%          
Maximum [Member] | Base Rate [Member] | Amended Credit Facility [Member] | Tranche C Term Loan [Member] | Subsequent Event [Member] | Unsecured Debt [Member]            
Subsequent Event [Line Items]            
Leverage based margin threshold 1.25%          
Elective leverage based margin threshold 1.45%