REPORTABLE SEGMENTS (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment home	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segments
Same store communities | home									37,959
Reportable Segments
Number of reportable segments | segment									2
Community Threshold, Percent Occupancy Threshold									90%
Time to maintain percent occupancy to be considered a community									3 months
Practical expedient, single lease component									true
Capital expenditures and development									$ 195,981	$ 214,898	$ 369,029
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Rental income	$ 302,745	$ 289,008	$ 278,463	$ 267,922	$ 264,732	$ 263,256	$ 256,634	$ 250,483	1,138,138	1,035,105	984,309
Reconciling items:
Joint venture management and other fees									$ 14,055	$ 11,754	$ 11,482
Type of revenue									udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember
Property management									$ (32,721)	$ (28,465)	$ (27,068)
Other operating expenses									(13,932)	(12,100)	(9,060)
Real estate depreciation and amortization									(501,257)	(429,006)	(430,054)
General and administrative									(51,533)	(46,983)	(48,566)
Casualty-related (charges)/recoveries, net									(474)	(2,121)	(4,335)
Other depreciation and amortization									(6,666)	(6,673)	(6,408)
Gain/(loss) on sale of real estate owned									5,282	136,197	43,404
Income/(loss) from unconsolidated entities									137,873	(5,055)	31,257
Interest expense									(170,917)	(134,168)	(128,711)
Interest and other income/(expense), net									15,404	6,735	1,971
Tax (provision)/benefit, net									(3,838)	(688)	240
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership									(14,426)	(18,215)	(10,933)
Net (income)/loss attributable to noncontrolling interests									(188)	(221)	(164)
Net income/(loss) attributable to UDR, Inc.									184,965	203,106	121,558
Reportable apartment home segment assets:
Total segment assets	12,602,101				10,196,159				12,602,101	10,196,159
Accumulated depreciation	(4,131,353)				(3,654,160)				(4,131,353)	(3,654,160)
Total real estate owned, net of accumulated depreciation	8,470,748				6,541,999				8,470,748	6,541,999
Reconciling items:
Cash and cash equivalents	8,106				185,216				8,106	185,216	2,038	$ 2,112
Restricted cash	25,185				23,675				25,185	23,675	19,792	$ 19,994
Notes receivable, net	153,650				42,259				153,650	42,259
Investment in and advances to unconsolidated joint ventures, net	588,262				780,869				588,262	780,869
Operating lease right-of-use assets	204,225								204,225
Other assets	186,296				137,710				186,296	137,710
Total consolidated assets	9,636,472				7,711,728				9,636,472	7,711,728
Same Store Communities West Region
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue									392,456	377,259	361,277
Other revenue									31,045	28,493	27,493
Rental income									423,501	405,752	388,770
Reportable apartment home segment NOI									321,890	306,307	291,265
Reportable apartment home segment assets:
Total segment assets	3,810,672				3,763,366				3,810,672	3,763,366
Same Store Communities Mid-Atlantic Region
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue									210,391	204,733	199,206
Other revenue									17,049	15,717	14,951
Rental income									227,440	220,450	214,157
Reportable apartment home segment NOI									159,665	153,670	150,126
Reportable apartment home segment assets:
Total segment assets	2,350,341				2,317,369				2,350,341	2,317,369
Same Store Communities Southeast Region
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue									113,175	109,189	104,106
Other revenue									13,557	13,045	12,361
Rental income									126,732	122,234	116,467
Reportable apartment home segment NOI									88,467	85,220	80,726
Reportable apartment home segment assets:
Total segment assets	806,830				779,310				806,830	779,310
Same Store Communities Northeast Region
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue									119,910	117,572	115,713
Other revenue									4,858	4,590	4,307
Rental income									124,768	122,162	120,020
Reportable apartment home segment NOI									83,832	84,059	83,569
Reportable apartment home segment assets:
Total segment assets	1,500,597				1,491,994				1,500,597	1,491,994
Same Store Communities Southwest Region
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue									54,516	52,970	51,949
Other revenue									5,312	5,281	5,152
Rental income									59,828	58,251	57,101
Reportable apartment home segment NOI									36,589	34,506	34,439
Reportable apartment home segment assets:
Total segment assets	456,140				447,305				456,140	447,305
Non-Mature communities/Other
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue									162,969	94,176	77,524
Other revenue									12,900	12,080	10,270
Rental income									175,869	106,256	87,794
Reportable apartment home segment NOI									117,860	68,353	58,378
Reportable apartment home segment assets:
Total segment assets	$ 3,677,521				$ 1,396,815				3,677,521	1,396,815
Total Communities
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue									1,053,417	955,899	909,775
Other revenue									84,721	79,206	74,534
Rental income									1,138,138	1,035,105	984,309
Reportable apartment home segment NOI									$ 808,303	$ 732,115	$ 698,503
Taxable REIT Subsidiaries
Reportable Segments
Management fee (as a percent)									2.875%