STOCKHOLDERS' EQUITY - Shares Rollforward (Details) - shares shares in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Issuance of common shares through public offering	7,500
Common Stock
Shares issued, beginning of period		275,546	267,822	267,259
Issuance/(forfeiture) of common and restricted shares, net		50	47	70
Issuance of common shares upon exercise of stock options			772
Issuance of common shares through public offering		7,500	7,150	87
Issuance of common shares though ATM program		6,988
Issuance of common shares through forward sales agreement		1,339
Repurchase of common shares			(593)
Conversion of Series E Cumulative Convertible shares				17
Shares issued, end of period		294,588	275,546	267,822
8.00% Series E Cumulative Convertible Preferred Stock
Shares issued, beginning of period		2,781	2,781	2,797
Conversion of Series E Cumulative Convertible shares				(16)
Shares issued, end of period		2,781	2,781	2,781
Series F
Shares issued, beginning of period		15,802	15,852	16,196
Forfeiture of Series F shares		(1,111)	(50)	(344)
Shares issued, end of period		14,691	15,802	15,852
Series F | Maximum
Forfeiture of Series F shares			(100)
United Dominion Realty L.P. | Common Stock
Adjustment for conversion of non-controlling interest of unitholders		1,969	11	8
UDR Lighthouse DownREIT L.P. | Common Stock
Adjustment for conversion of non-controlling interest of unitholders		1,196	337	381
UDR Lighthouse DownREIT L.P. | Series F
Forfeiture of Series F shares		(1,100)
Common Stock
Issuance of common shares through public offering		7,500