REPORTABLE SEGMENTS (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) home	Sep. 30, 2019 USD ($) home	Sep. 30, 2020 USD ($) home segment	Sep. 30, 2019 USD ($) home	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Segments
Same store communities | home	40,258	40,258	37,607	37,607
Reportable Segments
Number of reportable segments | segment			2
Condition for Community considered to have stabilized occupancy			90%
Time to maintain percent occupancy to be considered a community			3 months
Practical expedient, single lease component			true
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Rental income	$ 308,845	$ 289,008	$ 934,920	$ 835,393
Reconciling items:
Joint venture management and other fees	$ 1,199	$ 6,386	$ 3,861	$ 11,982
Type of revenue	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember
Property management	$ (8,879)	$ (8,309)	$ (26,879)	$ (24,018)
Other operating expenses	(5,543)	(2,751)	(16,609)	(11,132)
Real estate depreciation and amortization	(151,949)	(127,391)	(462,481)	(357,793)
General and administrative	(11,958)	(12,197)	(37,907)	(37,002)
Casualty-related (charges)/recoveries, net		1,088	(1,353)	842
Other depreciation and amortization	(3,887)	(1,619)	(7,939)	(4,953)
Gain/(loss) on sale of real estate owned			61,303	5,282
Income/(loss) from unconsolidated entities	2,940	12,713	14,328	19,387
Interest expense	(62,268)	(42,523)	(140,182)	(110,482)
Interest and other income/(expense), net	2,183	1,875	7,304	12,998
Tax (provision)/benefit, net	(187)	(1,499)	(1,877)	(3,836)
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership	1,990	(2,162)	(2,614)	(6,871)
Net (income)/loss attributable to noncontrolling interests	(31)	(56)	(71)	(145)
Net income/(loss) attributable to UDR, Inc.	(25,258)	27,204	37,734	87,326
Reportable apartment home segment assets:
Total segment assets	12,861,020		12,861,020		$ 12,602,101
Accumulated depreciation	(4,512,771)		(4,512,771)		(4,131,353)
Total real estate owned, net of accumulated depreciation	8,348,249		8,348,249		8,470,748
Reconciling items:
Cash and cash equivalents	927	1,895	927	1,895	8,106	$ 185,216
Restricted cash	23,273	21,646	23,273	21,646	25,185	$ 23,675
Notes receivable, net	156,996		156,996		153,650
Investment in and advances to unconsolidated joint ventures, net	646,355		646,355		588,262
Operating lease right-of-use assets	201,754		201,754		204,225
Other assets	173,834		173,834		186,296
Total consolidated assets	9,551,388		9,551,388		9,636,472
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	102,609	110,860	294,355	301,291
Other revenue	3,418	3,510	8,788	9,313
Rental income	106,027	114,370	303,143	310,604
Reportable apartment home segment NOI	77,361	86,159	226,538	235,925
Reportable apartment home segment assets:
Total segment assets	4,253,098		4,253,098		4,228,359
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	52,411	53,019	159,015	157,914
Other revenue	1,831	2,012	4,725	5,611
Rental income	54,242	55,031	163,740	163,525
Reportable apartment home segment NOI	37,258	38,483	113,913	114,892
Reportable apartment home segment assets:
Total segment assets	2,244,315		2,244,315		2,222,405
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	32,705	40,558	83,314	91,203
Other revenue	1,102	1,008	2,051	2,200
Rental income	33,807	41,566	85,365	93,403
Reportable apartment home segment NOI	18,981	27,962	52,020	63,012
Reportable apartment home segment assets:
Total segment assets	2,079,168		2,079,168		2,073,052
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	34,207	33,283	92,555	89,859
Other revenue	1,436	1,782	3,949	5,115
Rental income	35,643	35,065	96,504	94,974
Reportable apartment home segment NOI	23,714	24,033	66,029	66,301
Reportable apartment home segment assets:
Total segment assets	967,465		967,465		953,029
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	16,418	16,229	49,435	48,600
Other revenue	710	749	1,815	2,191
Rental income	17,128	16,978	51,250	50,791
Reportable apartment home segment NOI	10,496	10,449	32,019	31,221
Reportable apartment home segment assets:
Total segment assets	607,326		607,326		600,349
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	58,848	25,292	227,725	119,262
Other revenue	3,150	706	7,193	2,834
Rental income	61,998	25,998	234,918	122,096
Reportable apartment home segment NOI	43,322	16,563	158,331	81,716
Reportable apartment home segment assets:
Total segment assets	2,709,648		2,709,648		$ 2,524,907
Total Communities
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease revenue	297,198	279,241	906,399	808,129
Other revenue	11,647	9,767	28,521	27,264
Rental income	308,845	289,008	934,920	835,393
Reportable apartment home segment NOI	$ 211,132	$ 203,649	$ 648,850	$ 593,067
Taxable REIT Subsidiaries
Reportable Segments
Management fee (as a percent)			2.875%