UNCONSOLIDATED ENTITIES (UNITED DOMINION REALTY, L.P.) - Summary Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Operating income/(loss)	$ 8,021	$ 6,625	$ 11,388	$ 6,674
United Dominion Realty L.P.
Operating income/(loss)	(1,661)	(1,794)	(3,422)	(4,534)
UDR Lighthouse DownREIT L.P. | United Dominion Realty L.P.
Total real estate, net	1,070,653		1,070,653		$ 1,106,703
Cash and cash equivalents	20		20		20
Note receivable from the General Partner	220,937		220,937		222,853
Other assets	8,397		8,397		4,829
Total assets	1,300,007		1,300,007		1,334,405
Secured debt, net	425,859		425,859		427,592
Other liabilities	25,426		25,426		28,087
Liabilities	451,285		451,285		455,679
Total capital	848,722		848,722		$ 878,726
Total revenues	32,107	32,025	64,785	63,631
Property operating expenses	(12,680)	(12,751)	(25,989)	(25,847)
Real estate depreciation and amortization	(21,112)	(20,510)	(42,098)	(40,804)
Operating income/(loss)	(1,685)	(1,236)	(3,302)	(3,020)
Interest expense	(3,609)	(3,929)	(7,226)	(7,817)
Other income/(loss)	1,941	2,018	3,830	4,006
Net income /(loss)	$ (3,353)	$ (3,147)	$ (6,698)	$ (6,831)