Annual report pursuant to Section 13 and 15(d)

EARNINGS PER SHARE - Narrative (Details)

v3.3.1.900
EARNINGS PER SHARE - Narrative (Details)
 12 Months Ended
Dec. 31, 2015
unit / shares
shares
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] | OP units [Member]  
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]  
Minimum conversion period 1 year
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 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 236,265
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 423,800