Quarterly report pursuant to Section 13 or 15(d)

EARNINGS PER SHARE - Narrative (Details)

v3.7.0.1
EARNINGS PER SHARE - Narrative (Details)
 3 Months Ended
Mar. 31, 2017
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
Minimum conversion period 1 year
DownREIT Partnership [Member] | OP units [Member]  
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]  
Unit conversion ratio 1
Minimum conversion period 5 years
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 5 years
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 or market condition [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 437,799
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 260,400
OP units, DownREIT OP units, Subordinated performance units, DownREIT subordinated performance 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 50,000,000