JOINT VENTURES AND PARTNERSHIPS - Summary (Details)	1 Months Ended			12 Months Ended
	Jan. 31, 2020 USD ($)	Aug. 31, 2019 USD ($)	Jan. 31, 2019 USD ($) home	Dec. 31, 2019 USD ($) home property community	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 31, 2019	Sep. 30, 2018 item	Aug. 31, 2018 USD ($) item
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | community				148
Investment in unconsolidated entities					$ 585,490,000
Unconsolidated Joint Ventures
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities				$ 313,053,000	556,694,000
Unconsolidated Joint Venture Three Washington DC
Schedule of Equity Method Investments [Line Items]
Payment to acquire real estate		$ 184,000,000.0
UDR's Ownership Interest		100.00%					30.00%
Preferred Equity Investment 1641 Lincoln Santa Monica CA
Schedule of Equity Method Investments [Line Items]
Number of apartment homes									66
Investment in unconsolidated entities				$ 10,379,000	9,211,000
Rate				12.00%					12.00%
Years to Maturity				2 years 7 months 6 days
UDR commitment				$ 8,800,000
Income from investments				1,169,000	406,000
Preferred Equity Investment 1300 Fairmount Philadelphia, PA
Schedule of Equity Method Investments [Line Items]
Number of apartment homes | item									471
Investment in unconsolidated entities				$ 51,215,000	8,318,000
Years to Maturity				3 years 7 months 6 days
UDR commitment				$ 51,393,000
Income from investments				3,098,000	159,000
Preferred Equity Investment Essex Orlando, FL
Schedule of Equity Method Investments [Line Items]
Number of apartment homes | item								330
Investment in unconsolidated entities				$ 14,804,000	9,940,000
Rate				12.50%				12.50%
Years to Maturity				3 years 8 months 12 days
UDR commitment				$ 12,886,000
Income from investments				1,639,000	258,000
Preferred Equity Investment Oakland, CA
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities				$ 22,653,000
Rate				9.00%
Years to Maturity				4 years 3 months 18 days
UDR commitment				$ 27,250,000
Income from investments				1,067,000
Other Investment Ventures
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities				13,598,000	4,154,000
UDR commitment				18,000,000
Income from investments				$ 4,053,000	$ (267,000)	$ (30,000)
386 Home Operating Community In Anaheim
Schedule of Equity Method Investments [Line Items]
Number of apartment homes | home			386
Payment to acquire real estate			$ 33,500,000
UDR's Ownership Interest			100.00%	49.00%	49.00%
155 Home Operating Community in Seattle
Schedule of Equity Method Investments [Line Items]
Number of apartment homes | home			155
Payment to acquire real estate			$ 20,000,000.0
UDR's Ownership Interest			100.00%	49.00%	49.00%
Preferred Equity Investment Hillsboro Oregon
Schedule of Equity Method Investments [Line Items]
UDR's Ownership Interest				49.00%
Development Community
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities				$ 272,437,000	$ 224,175,000
Development Community | Unconsolidated Joint Venture UDR Met Life I Partnership
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property				1
Number of apartment homes | home				150
Investment in unconsolidated entities				$ 28,812,000	$ 30,839,000
UDR's Ownership Interest				50.00%	50.00%
Development Community | Preferred Equity Investment West Coast Development JV
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities				$ 17,064,000	$ 65,417,000
Rate				6.50%
Income from investments				$ (447,000)	865,000	23,230,000
Development Community | Preferred Equity Investment 1532 Harrison San Francisco, CA
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities				$ 30,585,000	24,986,000
Rate				11.00%
Years to Maturity				2 years 6 months
UDR commitment				$ 24,645,000
Income from investments				3,147,000	2,228,000	511,000
Development Community | Preferred Equity Investment 1200 Broadway Nashville TN
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities				$ 63,958,000	58,982,000
Rate				8.00%
Years to Maturity				2 years 9 months 18 days
UDR commitment				$ 55,558,000
Income from investments				4,888,000	2,970,000	370,000
Development Community | Other Investment The Portals Washington, DC
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities				$ 48,181,000	43,167,000
Rate				11.00%
Years to Maturity				1 year 4 months 24 days
UDR commitment				$ 38,559,000
Income from investments				$ 5,012,000	3,692,000	$ 839,000
Operating Community | Unconsolidated Joint Venture UDR MetLife II Partnership
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property				7
Number of apartment homes | home				1,250
Investment in unconsolidated entities				$ 150,893,000	$ 296,807,000
UDR's Ownership Interest				50.00%	50.00%
Operating Community | Unconsolidated Joint Venture Other MetLife
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property				5
Number of apartment homes | home				1,437
Investment in unconsolidated entities				$ 98,441,000	$ 115,668,000
UDR's Ownership Interest				50.60%	50.60%
Operating Community | Unconsolidated Joint Venture Vitruvian Park
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities					$ 71,730,000
UDR's Ownership Interest					50.00%
Operating Community | Unconsolidated Joint Venture Three Washington DC
Schedule of Equity Method Investments [Line Items]
Investment in unconsolidated entities					$ 5,507,000
UDR's Ownership Interest					30.00%
Operating Community | Unconsolidated Joint Venture West Coast Development JV
Schedule of Equity Method Investments [Line Items]
Number of real estate properties | property				1
Number of apartment homes | home				293
Investment in unconsolidated entities				$ 34,907,000	$ 36,143,000
UDR's Ownership Interest				47.00%	47.00%
Subsequent Event | Preferred Equity Investment Hillsboro Oregon
Schedule of Equity Method Investments [Line Items]
Payment to acquire real estate	$ 21,600,000
UDR's Ownership Interest	100.00%