NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Noncontrolling interests
Minimum holding period prior to redemption (in years)	1 year
Redeemable noncontrolling interests in the Operating Partnership
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership, beginning of year	$ 948,138	$ 909,482
Mark-to-market adjustment to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	(43,552)	(71,096)
Conversion of OP Units/DownREIT Units to Common Stock	13,328	14,544
Net income/(loss) attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	18,215	10,933	$ 27,282
Distributions to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	(32,798)	(31,427)
OP Units Issued	4,320
Vesting of Long-Term Incentive Plan Units	4,397	2,317
Allocation of other comprehensive income/(loss)	244	281
Redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership, end of year	972,740	948,138	909,482
Net income/(loss) attributable to noncontrolling interests	$ (175)	$ (147)	$ (322)
LTIP Units | Minimum
Redeemable noncontrolling interests in the Operating Partnership
Vesting period	1 year
LTIP Units | Maximum
Redeemable noncontrolling interests in the Operating Partnership
Vesting period	3 years