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INCOME/(LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands | 1 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Dec. 31, 2019 | Sep. 30, 2019 | Aug. 31, 2019 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Jul. 31, 2017
Antidilutive securities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net income/(loss) |  |  |  |  |  |  |  |  |  |  |  | $ 199,579 | $ 221,542 | $ 132,655 |
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership |  |  |  |  |  |  |  |  |  |  |  | (14,426) | (18,215) | (10,933) |
Net (income)/loss attributable to noncontrolling interests |  |  |  |  |  |  |  |  |  |  |  | (188) | (221) | (164) |
Net income/(loss) attributable to UDR, Inc. |  |  |  |  |  |  |  |  |  |  |  | 184,965 | 203,106 | 121,558 |
Distributions to preferred stockholders - Series E (Convertible) |  |  |  |  |  |  |  |  |  |  |  | (4,104) | (3,868) | (3,708) |
Net income/(loss) attributable to common stockholders |  |  |  |  |  |  |  | $ 81,168 | $ 17,639 | $ 19,630 | $ 80,801 | $ 180,861 | $ 199,238 | $ 117,850 |
Denominator for earnings per share - basic and diluted: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average common shares outstanding |  |  |  |  |  |  |  |  |  |  |  | 285,509,000 | 268,513,000 | 267,567,000 |
Non-vested restricted stock awards |  |  |  |  |  |  |  |  |  |  |  | (262,000) | (334,000) | (543,000) |
Denominator for basic income/(loss) per share |  |  |  | 293,107,000 | 288,706,000 | 281,960,000 | 277,002,000 | 270,107,000 | 267,727,000 | 267,311,000 | 267,546,000 | 285,247,000 | 268,179,000 | 267,024,000 |
Denominator for diluted income/(loss) per share |  |  |  | 294,073,000 | 289,529,000 | 282,575,000 | 277,557,000 | 270,755,000 | 268,861,000 | 268,890,000 | 269,208,000 | 286,015,000 | 269,483,000 | 268,830,000 |
Income/(loss) per weighted average common share - basic |  |  |  | $ 0.33 | $ 0.09 | $ 0.12 | $ 0.08 | $ 0.30 | $ 0.07 | $ 0.07 | $ 0.30 | $ 0.63 | $ 0.74 | $ 0.44 |
Income/(loss) per weighted average common share - diluted |  |  |  | $ 0.33 | $ 0.09 | $ 0.12 | $ 0.08 | $ 0.30 | $ 0.07 | $ 0.07 | $ 0.30 | $ 0.63 | $ 0.74 | $ 0.44 |
Number of shares authorized | 350,000,000 |  |  | 350,000,000 |  |  |  | 350,000,000 |  |  |  | 350,000,000 | 350,000,000 |  |
Number of shares sold |  |  | 7,500,000 |  |  |  |  |  |  |  |  |  |  |  |
Aggregate gross proceeds |  |  | $ 349,900 |  |  |  |  |  |  |  |  | $ 725,315 | $ 299,825 |  |
Weighted average price per share |  |  | $ 46.65 |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from the issuance of common shares through public offering, net |  |  | $ 349,900 |  |  |  |  |  |  |  |  | 725,315 | 299,825 |  |
Aggregate net proceeds from sales, after deducting related costs |  |  | $ 349,800 |  |  |  |  |  |  |  |  | $ 725,315 | $ 299,825 |  |
OP/DownREIT Units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Antidilutive securities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Antidilutive securities |  |  |  |  |  |  |  |  |  |  |  | 22,773,000 | 24,548,000 | 24,821,000 |
Convertible preferred stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Antidilutive securities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Antidilutive securities |  |  |  |  |  |  |  |  |  |  |  | 3,011,000 | 3,011,000 | 3,021,000 |
stock options, unvested LTIP Units, and unvested restricted stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Antidilutive securities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Antidilutive securities |  |  |  |  |  |  |  |  |  |  |  | 768,000 | 1,304,000 | 1,806,000 |
Denominator for earnings per share - basic and diluted: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Incremental shares issuable from assumed conversion of stock options, unvested LTIP Units, unvested restricted stock, and shares issuable upon settlement of forward purchase agreements |  |  |  |  |  |  |  |  |  |  |  | 768,000 | 1,304,000 | 1,806,000 |
ATM |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Denominator for earnings per share - basic and diluted: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares authorized |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20,000,000.0
Number of shares sold |  |  |  |  |  |  |  |  |  |  |  | 7,000,000.0 |  |  |
Aggregate gross proceeds |  |  |  |  |  |  |  |  |  |  |  | $ 316,500 |  |  |
Weighted average price per share |  |  |  |  |  |  |  |  |  |  |  | $ 45.29 |  |  |
Proceeds from the issuance of common shares through public offering, net |  |  |  |  |  |  |  |  |  |  |  | $ 316,500 |  |  |
Commissions paid to sales agents |  |  |  |  |  |  |  |  |  |  |  | 4,000 |  |  |
Aggregate net proceeds from sales, after deducting related costs |  |  |  |  |  |  |  |  |  |  |  | $ 312,300 |  |  |
Shares of common stock available for future issuance | 11,700,000 |  |  | 11,700,000 |  |  |  |  |  |  |  | 11,700,000 |  |  |
Forward Sales Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Denominator for earnings per share - basic and diluted: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares authorized |  | 1,300,000 |  |  | 1,300,000 |  |  |  |  |  |  |  |  |  |
Number of shares sold | 1,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate gross proceeds | $ 63,500 |  |  |  |  |  |  |  |  |  |  |  | $ 63,200 |  |
Weighted average price per share | $ 47.41 | $ 47.68 |  |  |  |  |  |  |  |  |  |  |  |  |
Forward price |  |  |  |  |  |  |  |  |  |  |  |  | $ 47.41 |  |
Proceeds from the issuance of common shares through public offering, net | $ 63,500 |  |  |  |  |  |  |  |  |  |  |  | $ 63,200 |  |
Commissions paid to sales agents | 600 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate net proceeds from sales, after deducting related costs | $ 63,200 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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