Quarterly report pursuant to Section 13 or 15(d)

NONCONTROLLING INTERESTS - Narrative (Details)

v3.7.0.1
NONCONTROLLING INTERESTS - Narrative (Details)
6 Months Ended
Jun. 30, 2017
unit / shares
$ / shares
shares
Dec. 31, 2016
$ / shares
Class of Stock [Line Items]    
Common shares of beneficial interest, par value (in dollars per share) | $ / shares $ 0.01 $ 0.01
OP units [Member] | NSA OP, LP [Member]    
Class of Stock [Line Items]    
Unit conversion ratio | unit / shares 1  
Minimum conversion period 1 year  
Redemptions of units (in shares) 1,153,518  
OP units [Member] | NSA OP, LP [Member] | Self Storage Properties [Member]    
Class of Stock [Line Items]    
Issuance of units, (in shares) 473,533  
OP units [Member] | DownREIT Partnership [Member]    
Class of Stock [Line Items]    
Unit conversion ratio | unit / shares 1  
Minimum conversion period 5 years  
Subordinated performance units [Member] | NSA OP, LP [Member]    
Class of Stock [Line Items]    
Unit conversion, lock out period 2 years  
Subordinated performance units [Member] | NSA OP, LP [Member] | Self Storage Properties [Member]    
Class of Stock [Line Items]    
Issuance of units, (in shares) 96,394  
Subordinated performance units [Member] | NSA OP, LP [Member] | Affiliate of Personal Mini [Member]    
Class of Stock [Line Items]    
Issuance of units, (in shares) 300,043  
Subordinated performance units [Member] | DownREIT Partnership [Member]    
Class of Stock [Line Items]    
Unit conversion ratio | unit / shares 1  
Minimum conversion period 5 years  
LTIP units [Member]    
Class of Stock [Line Items]    
Issuance of units, (in shares) 219,299  
LTIP units [Member] | NSA OP, LP [Member]    
Class of Stock [Line Items]    
Unit conversion ratio | unit / shares 1  
Redemptions of units (in shares) 828,881  
Conversion of units (in shares) 828,881