Quarterly report pursuant to Section 13 or 15(d)

EARNINGS PER SHARE - Narrative (Details)

v3.3.0.814
EARNINGS PER SHARE - Narrative (Details)
 3 Months Ended 9 Months Ended
Sep. 30, 2015
shares
Sep. 30, 2015
unit / shares
shares
NSA OP, LP [Member] | LTIP units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Weighted average outstanding equity interests excluded from computation of earnings (in units) | shares 364,817 364,817
NSA OP, LP [Member] | OP units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Unit conversion ratio   1
DownREIT Partnership [Member] | OP units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Unit conversion ratio   1
NSA OP, LP And DownREIT Partnership [Member] | Subordinated performance units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Minimum conversion period   2 years
Unit conversion ratio   1
Participating Regional Operator [Member] | Affiliated Entity [Member] | NSA OP, LP [Member] | LTIP units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Weighted average outstanding equity interests excluded from computation of earnings (in units) | shares 522,900 522,900