UNCONSOLIDATED ENTITIES (UNITED DOMINION REALTY, L.P.) - Summary Financial Information (Details) - UDR Lighthouse DownREIT L.P. - United Dominion Realty L.P. - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Total real estate, net	$ 1,088,125		$ 1,106,703
Cash and cash equivalents	20		20
Note receivable from the General Partner	220,622		222,853
Other assets	5,312		4,829
Total assets	1,314,079		1,334,405
Secured debt, net	426,724		427,592
Other liabilities	23,628		28,087
Liabilities	450,352		455,679
Total capital	863,727		$ 878,726
Total revenues	32,678	$ 31,606
Property operating expenses	(13,309)	(13,096)
Real estate depreciation and amortization	(20,986)	(20,294)
Operating income/(loss)	(1,617)	(1,784)
Interest expense	(3,618)	(3,888)
Other income/(loss)	1,889	1,988
Net income /(loss)	$ (3,346)	$ (3,684)