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JOINT VENTURES AND PARTNERSHIPS - Summary (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) home community property	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) home community property	Jun. 30, 2019 USD ($)	Jul. 29, 2020 USD ($) home	Feb. 29, 2020 USD ($) home	Jan. 31, 2020 home	Dec. 31, 2019 USD ($)
Unconsolidated entities
Investment in unconsolidated entities	$ 594,275		$ 594,275					$ 585,490
Number of real estate properties \| community	148		148
Financial information relating to unconsolidated joint ventures operations
Operating income/(loss)	$ 8,021	$ 6,625	$ 11,388	$ 6,674
Unconsolidated Joint Ventures
Combined summary of balance sheets relating to unconsolidated joint ventures
Total real estate, net	1,922,313		1,922,313					1,901,081
Cash and cash equivalents	30,656		30,656					29,823
Other assets	216,356		216,356					172,941
Total assets	2,169,325		2,169,325					2,103,845
Third party debt, net	1,156,834		1,156,834					1,148,048
Accounts payable and accrued liabilities	46,057		46,057					55,114
Total liabilities	1,202,891		1,202,891					1,203,162
Total equity	966,434		966,434					$ 900,683
Financial information relating to unconsolidated joint ventures operations
Total revenues	37,312	76,926	78,626	158,458
Property operating expenses	14,468	29,256	29,765	59,568
Real estate depreciation and amortization	16,913	28,054	33,156	57,634
Operating income/(loss)	5,931	19,616	15,705	41,256
Interest expense	(10,149)	(21,606)	(20,496)	(43,530)
Gain (loss) on sale of property		18,357		18,357
Net unrealized gain/(loss) on held investments	29,312		29,312
Other income/(loss)	117	9	109	1,634
Net income /(loss)	25,211	16,376	24,630	17,717
Preferred Equity Investment Hillsboro Oregon
Unconsolidated entities
Number of apartment homes \| home							276
UDR's Ownership Interest							100.00%	49.00%
Preferred Equity Investment Thousand Oaks
Unconsolidated entities
Number of apartment homes \| home						142
Rate						9.00%
Preferred Equity Investment Thousand Oaks \| Maximum
Unconsolidated entities
UDR commitment						$ 20,100
Preferred Equity Investment Queens, New York
Unconsolidated entities
Number of apartment homes \| home					534
UDR commitment					$ 40,000
Rate					13.00%
Operating Community
Unconsolidated entities
Investment in unconsolidated entities	302,588		302,588					$ 313,053
Income from investments	$ (3,016)	2,052	$ (5,453)	(1,835)
Operating Community \| Unconsolidated Joint Venture UDR Met Life I Partnership
Unconsolidated entities
Number of apartment homes \| home	150		150
Investment in unconsolidated entities	$ 27,927		$ 27,927					$ 28,812
UDR's Ownership Interest	50.00%		50.00%					50.00%
Number of real estate properties \| property	1		1
Income from investments	$ (658)	(548)	$ (1,112)	(1,124)
Operating Community \| Unconsolidated Joint Venture UDR MetLife II Partnership
Unconsolidated entities
Number of apartment homes \| home	1,250		1,250
Investment in unconsolidated entities	$ 149,971		$ 149,971					$ 150,893
UDR's Ownership Interest	50.00%		50.00%					50.00%
Number of real estate properties \| property	7		7
Income from investments	$ 10	776	$ (81)	1,210
Operating Community \| Unconsolidated Joint Venture Other MetLife
Unconsolidated entities
Number of apartment homes \| home	1,437		1,437
Investment in unconsolidated entities	$ 90,262		$ 90,262					$ 98,441
UDR's Ownership Interest	50.60%		50.60%					50.60%
Number of real estate properties \| property	5		5
Income from investments	$ (2,312)	(1,684)	$ (4,124)	(3,461)
Operating Community \| Unconsolidated Joint Venture West Coast Development JV
Unconsolidated entities
Number of apartment homes \| home	293		293
Investment in unconsolidated entities	$ 34,428		$ 34,428					$ 34,907
UDR's Ownership Interest	47.00%		47.00%					47.00%
Number of real estate properties \| property	1		1
Income from investments	$ (56)	(359)	$ (136)	(507)
Operating Community \| Sold Joint Ventures
Unconsolidated entities
Income from investments		3,867		2,047
Development Community \| Preferred Equity Investment Hillsboro Oregon
Unconsolidated entities
Investment in unconsolidated entities								$ 17,064
Rate	6.50%		6.50%
Income from investments		(10)	$ (46)	(171)
Development Community \| Preferred Equity Investment 1532 Harrison San Francisco, CA
Unconsolidated entities
Investment in unconsolidated entities	$ 32,282		32,282					30,585
UDR commitment	$ 24,645		$ 24,645
Rate	11.00%		11.00%
Years to Maturity			2 years
Income from investments	$ 846	774	$ 1,682	1,522
Participating Loan Years to Maturity			2 years
Development Community \| Preferred Equity Investment 1200 Broadway Nashville TN
Unconsolidated entities
Investment in unconsolidated entities	66,575		$ 66,575					63,958
UDR commitment	$ 55,558		$ 55,558
Rate	8.00%		8.00%
Years to Maturity			2 years 3 months 18 days
Income from investments	$ 1,306	1,206	$ 2,587	2,375
Participating Loan Years to Maturity			2 years 3 months 18 days
Development Community \| Preferred Equity Investment 1641 Lincoln Santa Monica CA
Unconsolidated entities
Investment in unconsolidated entities	11,016		$ 11,016					10,379
UDR commitment	$ 8,800		$ 8,800
Rate	12.00%		12.00%
Years to Maturity			2 years 1 month 6 days
Income from investments	$ 323	287	$ 637	562
Participating Loan Years to Maturity			2 years 1 month 6 days
Development Community \| Preferred Equity Investment 1300 Fairmount Philadelphia, PA
Unconsolidated entities
Investment in unconsolidated entities	57,031		$ 57,031					51,215
UDR commitment	51,393		$ 51,393
Years to Maturity			3 years 1 month 6 days
Income from investments	1,191	519	$ 2,357	794
Participating Loan Years to Maturity			3 years 1 month 6 days
Development Community \| Preferred Equity Investment Essex Orlando, FL
Unconsolidated entities
Investment in unconsolidated entities	15,751		$ 15,751					14,804
UDR commitment	$ 12,886		$ 12,886
Rate	12.50%		12.50%
Years to Maturity			3 years 2 months 12 days
Income from investments	$ 481	407	$ 947	739
Participating Loan Years to Maturity			3 years 2 months 12 days
Development Community \| Preferred Equity Investment Modera Lake Merritt, Oakland
Unconsolidated entities
Investment in unconsolidated entities	29,562		$ 29,562					22,653
UDR commitment	$ 27,250		$ 27,250
Rate	9.00%		9.00%
Years to Maturity			3 years 9 months 18 days
Income from investments	$ 652	256	$ 1,226	256
Participating Loan Years to Maturity			3 years 9 months 18 days
Development Community \| Preferred Equity Investment Thousand Oaks, CA
Unconsolidated entities
Investment in unconsolidated entities	8,872		$ 8,872
UDR commitment	$ 20,059		$ 20,059
Rate	9.00%		9.00%
Years to Maturity			4 years 8 months 12 days
Income from investments	$ 153		$ 177
Participating Loan Years to Maturity			4 years 8 months 12 days
Development Community \| Other Investment The Portals Washington, DC
Unconsolidated entities
Investment in unconsolidated entities	50,713		$ 50,713					48,181
UDR commitment	$ 38,559		$ 38,559
Rate	11.00%		11.00%
Years to Maturity			10 months 24 days
Income from investments	$ 1,389	1,234	$ 2,724	2,407
Participating Loan Years to Maturity			10 months 24 days
Development Community \| Other Investment Ventures
Unconsolidated entities
Investment in unconsolidated entities	19,885		$ 19,885					13,598
UDR commitment	34,500		34,500
Income from investments	4,696	(100)	4,550	25
Development Community \| Preferred Equity Investments and Other Investments
Unconsolidated entities
Investment in unconsolidated entities	291,687		291,687					$ 272,437
Income from investments	$ 11,037	$ 4,573	$ 16,841	$ 8,509