Quarterly report pursuant to Section 13 or 15(d)

EARNINGS PER SHARE - Narrative (Details)

v3.5.0.2
EARNINGS PER SHARE - Narrative (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2016
shares
Sep. 30, 2016
unit / shares
shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Weighted average outstanding equity interests excluded from computation of earnings (in units) | shares 49,800,000  
NSA OP, LP [Member] | OP units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Unit conversion ratio | unit / shares   1
DownREIT Partnership [Member] | OP units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Unit conversion ratio | unit / shares   1
NSA OP, LP And DownREIT Partnership [Member] | Subordinated performance units [Member]    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Unit conversion ratio | unit / shares   1
Minimum conversion period   2 years
Long-Term Incentive Plan Unit Based On Service [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 386,713 386,713
Long-Term Incentive Plan Unit Based On Future Acquisitions [Member] | Participating Regional Operator [Member] | Management [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 397,600 271,400