INCOME/(LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jul. 31, 2017
Antidilutive securities
Net income/(loss)	$ (27,217)	$ 29,422	$ 40,419	$ 94,342
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	1,990	(2,162)	(2,614)	(6,871)
Net (income)/loss attributable to noncontrolling interests	(31)	(56)	(71)	(145)
Net income/(loss) attributable to UDR, Inc.	(25,258)	27,204	37,734	87,326
Distributions to preferred stockholders - Series E (Convertible)	(1,051)	(1,031)	(3,179)	(3,073)
Net income/(loss) attributable to common stockholders	$ (26,309)	$ 26,173	$ 34,555	$ 84,253
Denominator for earnings per share - basic and diluted:
Weighted average common shares outstanding	294,972,000	288,957,000	294,891,000	282,866,000
Non-vested restricted stock awards	(259,000)	(251,000)	(264,000)	(268,000)
Denominator for basic income/(loss) per share	294,713,000	288,706,000	294,627,000	282,598,000
Incremental shares issuable from assumed conversion of unvested LTIP Units and unvested restricted stock	290,000	823,000	311,000	694,000
Denominator for diluted income/(loss) per share	295,003,000	289,529,000	294,938,000	283,292,000
Income/(loss) per weighted average common share - basic	$ (0.09)	$ 0.09	$ 0.12	$ 0.30
Income/(loss) per weighted average common share - diluted	$ (0.09)	$ 0.09	$ 0.12	$ 0.30
Number of shares authorized	350,000,000		350,000,000		350,000,000
Aggregate gross proceeds				$ 662,009
Proceeds from the issuance of common shares through public offering, net				662,009
Aggregate net proceeds from sales, after deducting related costs		$ 449,137		$ 662,009
Repurchase of common shares	600,000		600,000
Average price of shares repurchased (in dollars per share)	$ 33.11		$ 33.11
Total consideration	$ 19,800		$ 19,795
OP/DownREIT Units
Antidilutive securities
Antidilutive securities	22,321,000	22,211,000	22,312,000	23,068,000
Convertible preferred stock
Antidilutive securities
Antidilutive securities	2,918,000	3,011,000	2,960,000	3,011,000
Unvested LTIP Units and unvested restricted stock
Antidilutive securities
Antidilutive securities	290,000	823,000	311,000	694,000
ATM
Denominator for earnings per share - basic and diluted:
Number of shares authorized						20,000,000.0
Shares of common stock available for future issuance	11,700,000		11,700,000
Forward Sales Agreement
Denominator for earnings per share - basic and diluted:
Number of shares authorized	2,100,000		2,100,000
Weighted average price per share			$ 49.56
Shares settled			0