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 6 Months Ended
Jun. 30, 2017
shares
Jun. 30, 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 diluted earnings per share (in units) | shares 410,825 410,825
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 diluted earnings per share (in units) | shares 236,000 236,000
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 diluted earnings per share (in units) | shares 50,300,000 50,200,000