Quarterly report pursuant to Section 13 or 15(d)

NONCONTROLLING INTERESTS - Equity Interests (Details)

v3.4.0.3
NONCONTROLLING INTERESTS - Equity Interests (Details) - shares
3 Months Ended
Mar. 31, 2016
Dec. 31, 2015
Partnership Subsidiaries [Member]    
Noncontrolling Interest [Line Items]    
Outstanding equity interest (in shares) 41,139,604 39,865,541
OP units [Member] | NSA OP, LP [Member]    
Noncontrolling Interest [Line Items]    
Outstanding equity interest (in shares) 22,528,274 21,556,006
OP units [Member] | DownREIT Partnership [Member]    
Noncontrolling Interest [Line Items]    
Outstanding equity interest (in shares) 1,834,786 1,834,786
Subordinated performance units [Member] | NSA OP, LP [Member]    
Noncontrolling Interest [Line Items]    
Outstanding equity interest (in shares) 9,441,708 9,302,989
Subordinated performance units [Member] | DownREIT Partnership [Member]    
Noncontrolling Interest [Line Items]    
Outstanding equity interest (in shares) 4,386,999 4,386,999
LTIP units [Member]    
Noncontrolling Interest [Line Items]    
Compensatory LTIPs issued (in shares) 163,076  
LTIP units [Member] | NSA OP, LP [Member]    
Noncontrolling Interest [Line Items]    
Outstanding equity interest (in shares) 2,947,837 2,784,761