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JOINT VENTURES AND PARTNERSHIPS - Summary (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) community property home	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) community property home	Jun. 30, 2018 USD ($)	Apr. 30, 2019 community	Dec. 31, 2018 USD ($)	Sep. 30, 2018 item	Aug. 31, 2018 item	Sep. 30, 2017 item	Dec. 31, 2015 community
Unconsolidated entities
Investment in unconsolidated entities	$ 769,000		$ 769,000			$ 780,869
Number of real estate properties \| community	135		135
Financial information relating to unconsolidated joint ventures operations
Operating income/(loss)	$ 6,625	$ (2,032)	$ 6,674	$ (3,709)
Unconsolidated Joint Ventures
Unconsolidated entities
Investment in unconsolidated entities	547,315		547,315			556,694
Combined summary of balance sheets relating to unconsolidated joint ventures
Total real estate, net	3,065,052		3,065,052			3,311,034
Assets held for disposition	124,037		124,037
Cash and cash equivalents	41,192		41,192			49,867
Other assets	143,228		143,228			124,428
Total assets	3,373,509		3,373,509			3,485,329
Third party debt, net	1,886,009		1,886,009			2,125,350
Liabilities held for disposition	130,938		130,938
Accounts payable and accrued liabilities	65,565		65,565			71,272
Total liabilities	2,082,512		2,082,512			2,196,622
Total equity	1,290,997		1,290,997			1,288,707
Financial information relating to unconsolidated joint ventures operations
Total revenues	76,926	70,980	158,458	138,937
Property operating expenses	29,256	28,402	59,568	55,339
Real estate depreciation and amortization	28,054	28,670	57,634	55,518
Operating income/(loss)	19,616	13,908	41,256	28,080
Interest expense	(21,606)	(21,665)	(43,530)	(41,071)
Gain (loss) on sale of property	18,357		18,357
Other income/(loss)	9	106	1,634	101
Net income /(loss)	16,376	(7,651)	17,717	(12,890)
Unconsolidated Joint Venture West Coast Development JV
Unconsolidated entities
Investment in unconsolidated entities	$ 52,700		$ 52,700			101,600
Preferred Equity Investment West Coast Development JV
Unconsolidated entities
UDR's Ownership Interest										48.00%
Number of real estate properties \| community										5
Rate	6.50%		6.50%							6.50%
Preferred Equity Investment 1200 Broadway Nashville TN
Unconsolidated entities
Number of apartment homes \| item									313
Rate									8.00%
Preferred Equity Investment 1641 Lincoln Santa Monica CA
Unconsolidated entities
Number of apartment homes \| item								66
Rate								12.00%
Preferred Equity Investment 1300 Fairmount Philadelphia, PA
Unconsolidated entities
Number of apartment homes \| item								471
Preferred Equity Investment Essex Orlando, FL
Unconsolidated entities
Number of apartment homes \| item							330
Rate							12.50%
Preferred Equity Investment Modera Lake Merritt, Oakland
Unconsolidated entities
Number of apartment homes \| community					173
Rate					9.00%
Operating Community \| Unconsolidated Joint Venture UDR Met Life I Partnership
Unconsolidated entities
Number of apartment homes \| home	150		150
Investment in unconsolidated entities	$ 30,292		$ 30,292			$ 30,839
UDR's Ownership Interest	50.00%		50.00%			50.00%
Number of real estate properties \| property	1		1
Operating Community \| Unconsolidated Joint Venture UDR MetLife II Partnership
Unconsolidated entities
Number of apartment homes \| home	4,059		4,059
Investment in unconsolidated entities	$ 302,236		$ 302,236			$ 296,807
UDR's Ownership Interest	50.00%		50.00%			50.00%
Number of real estate properties \| property	18		18
Operating Community \| Unconsolidated Joint Venture Other MetLife
Unconsolidated entities
Number of apartment homes \| home	1,437		1,437
Investment in unconsolidated entities	$ 107,350		$ 107,350			$ 115,668
UDR's Ownership Interest	50.60%		50.60%			50.60%
Number of real estate properties \| property	5		5
Operating Community \| Unconsolidated Joint Venture Vitruvian Park
Unconsolidated entities
Number of apartment homes \| home	1,879		1,879
Investment in unconsolidated entities	$ 74,049		$ 74,049			$ 71,730
UDR's Ownership Interest	50.00%		50.00%			50.00%
Number of real estate properties \| property	4		4
Operating Community \| Unconsolidated Joint Venture Three Washington DC
Unconsolidated entities
Number of apartment homes \| home	443		443
Investment in unconsolidated entities	$ (2,006)		$ (2,006)			$ 5,507
UDR's Ownership Interest	30.00%		30.00%			30.00%
Number of real estate properties \| property	2		2
Operating Community \| Unconsolidated Joint Venture West Coast Development JV
Unconsolidated entities
Number of apartment homes \| home	293		293
Investment in unconsolidated entities	$ 35,394		$ 35,394			$ 36,143
UDR's Ownership Interest	47.00%		47.00%			47.00%
Number of real estate properties \| property	1		1
Development Community
Unconsolidated entities
Investment in unconsolidated entities	$ 221,685		$ 221,685			$ 224,175
Development Community \| Unconsolidated Joint Venture Vitruvian Park
Unconsolidated entities
Number of real estate properties \| property	1		1
Development Community \| Preferred Equity Investment West Coast Development JV
Unconsolidated entities
Investment in unconsolidated entities	$ 17,295		$ 17,295			65,417
Rate	6.50%		6.50%
Income from investments	$ (10)	153	$ (171)	949
Development Community \| Preferred Equity Investment 1532 Harrison San Francisco, CA
Unconsolidated entities
Investment in unconsolidated entities	28,943		28,943			24,986
UDR commitment	$ 24,645		$ 24,645
Rate	11.00%		11.00%
Years to Maturity			3 years
Income from investments	$ 774	430	$ 1,522	771
Development Community \| Preferred Equity Investment 1200 Broadway Nashville TN
Unconsolidated entities
Investment in unconsolidated entities	61,395		61,395			58,982
UDR commitment	$ 55,558		$ 55,558
Rate	8.00%		8.00%
Years to Maturity			3 years 3 months 18 days
Income from investments	$ 1,206	603	$ 2,375	1,011
Development Community \| Preferred Equity Investment 1641 Lincoln Santa Monica CA
Unconsolidated entities
Investment in unconsolidated entities	9,773		9,773			9,211
UDR commitment	$ 8,800		$ 8,800
Rate	12.00%		12.00%
Years to Maturity			3 years 1 month 6 days
Income from investments	$ 287		$ 562
Development Community \| Preferred Equity Investment 1300 Fairmount Philadelphia, PA
Unconsolidated entities
Investment in unconsolidated entities	23,373		23,373			8,318
UDR commitment	51,393		$ 51,393
Years to Maturity			4 years 1 month 6 days
Income from investments	519		$ 794
Development Community \| Preferred Equity Investment Essex Orlando, FL
Unconsolidated entities
Investment in unconsolidated entities	13,905		13,905			9,940
UDR commitment	$ 12,886		$ 12,886
Rate	12.50%		12.50%
Years to Maturity			4 years 2 months 12 days
Income from investments	$ 407		$ 739
Development Community \| Preferred Equity Investment Modera Lake Merritt, Oakland
Unconsolidated entities
Investment in unconsolidated entities	14,549		14,549
UDR commitment	$ 27,250		$ 27,250
Rate	9.00%		9.00%
Years to Maturity			5 years
Income from investments	$ 256		$ 256
Development Community \| Other Investment The Portals Washington, DC
Unconsolidated entities
Investment in unconsolidated entities	45,574		45,574			43,167
UDR commitment	$ 38,559		$ 38,559
Rate	11.00%		11.00%
Years to Maturity			1 year 10 months 24 days
Income from investments	$ 1,234	829	$ 2,407	1,508
Development Community \| Other Investment Ventures
Unconsolidated entities
Investment in unconsolidated entities	6,878		6,878			$ 4,154
UDR commitment	18,000		18,000
Income from investments	$ (100)	$ (95)	$ 25	$ (185)
Land Parcel \| Unconsolidated Joint Venture Vitruvian Park
Unconsolidated entities
Number of real estate properties \| property	4		4