REPORTABLE SEGMENTS (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) segment item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segments
Same store communities | item									37,673
Reportable Segments
Number of reportable segments | segment									2
Capital expenditures and development									$ 214,898	$ 369,029	$ 339,813
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease Revenue	$ 264,732	$ 263,256	$ 256,634	$ 250,483	$ 250,116	$ 248,264	$ 244,658	$ 241,271	1,035,105	984,309	948,461
Reportable apartment home segment NOI									732,115	698,503	673,085
Reconciling items:
Joint venture management and other fees									$ 11,754	$ 11,482	$ 11,400
Type of revenue									udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember
Property management									$ (28,465)	$ (27,068)	$ (26,083)
Other operating expenses									(12,100)	(9,060)	(7,649)
Real estate depreciation and amortization									(429,006)	(430,054)	(419,615)
General and administrative									(46,983)	(48,566)	(49,761)
Casualty-related (charges)/recoveries, net									(2,121)	(4,335)	(732)
Other depreciation and amortization									(6,673)	(6,408)	(6,023)
Income/(loss) from unconsolidated entities									(5,055)	31,257	52,234
Interest expense									(134,168)	(128,711)	(123,031)
Interest and other income/(expense), net									6,735	1,971	1,930
Gain/(loss) on sale of real estate owned									136,197	43,404	226,199
Tax (provision)/benefit, net									(688)	240	(11,574)
Net (income)/loss attributable to redeemable noncontrolling interests in the Operating Partnership and DownREIT Partnership									(18,215)	(10,933)	(27,282)
Net (income)/loss attributable to noncontrolling interests									(221)	(164)	(380)
Net income/(loss) attributable to UDR, Inc.									203,106	121,558	292,718
Reportable apartment home segment assets:
Total segment assets	10,196,159				10,177,206				10,196,159	10,177,206
Accumulated depreciation	(3,654,160)				(3,330,166)				(3,654,160)	(3,330,166)
Total real estate owned, net of accumulated depreciation	6,541,999				6,847,040				6,541,999	6,847,040
Reconciling items:
Cash and cash equivalents	185,216				2,038				185,216	2,038	2,112	$ 6,742
Restricted cash	23,675				19,792				23,675	19,792	19,994	20,798
Notes receivable, net	42,259				19,469				42,259	19,469
Investment in and advances to unconsolidated joint ventures, net	780,869				720,830				780,869	720,830
Other assets	137,710				124,104				137,710	124,104
Total consolidated assets	7,711,728				7,733,273				7,711,728	7,733,273
Same Communities
Reportable Segments
Capital expenditures and development									86,200	86,200	82,900
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									399,314	383,009	353,321
Reportable apartment home segment NOI									301,098	286,662	264,475
Reportable apartment home segment assets:
Total segment assets	3,666,169				3,630,164				3,666,169	3,630,164
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									220,450	214,157	208,223
Reportable apartment home segment NOI									153,670	150,126	144,508
Reportable apartment home segment assets:
Total segment assets	2,317,369				2,290,241				2,317,369	2,290,241
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									154,019	151,736	147,573
Reportable apartment home segment NOI									105,998	106,473	106,005
Reportable apartment home segment assets:
Total segment assets	1,874,616				1,865,762				1,874,616	1,865,762
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									122,234	116,467	111,318
Reportable apartment home segment NOI									85,220	80,726	76,359
Reportable apartment home segment assets:
Total segment assets	779,310				762,102				779,310	762,102
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									43,709	42,992	41,273
Reportable apartment home segment NOI									26,408	26,455	25,600
Reportable apartment home segment assets:
Total segment assets	297,681				292,074				297,681	292,074
Non-Mature communities/Other
Reportable Segments
Capital expenditures and development									5,800	5,700	13,400
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease Revenue									95,379	75,948	86,753
Reportable apartment home segment NOI									59,721	48,061	56,138
Reportable apartment home segment assets:
Total segment assets	1,261,014				1,336,863				$ 1,261,014	1,336,863
United Dominion Reality L.P.
Segments
Same store communities | item									16,216
Reportable Segments
Number of reportable segments | segment									2
Capital expenditures and development									$ 44,353	45,211	71,720
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease Revenue	108,523	109,539	107,266	106,592	107,431	105,253	104,088	102,605	431,920	419,377	404,415
Reportable apartment home segment NOI									317,380	306,841	297,121
Reconciling items:
Property management									(11,878)	(11,533)	(11,122)
Other operating expenses									(8,864)	(6,833)	(6,059)
Real estate depreciation and amortization									(143,481)	(152,473)	(147,074)
General and administrative									(16,889)	(17,875)	(18,808)
Casualty-related (charges)/recoveries, net									(951)	(1,922)	(484)
Income/(loss) from unconsolidated entities									43,496	(19,256)	(37,425)
Interest expense									(22,835)	(30,366)	(30,067)
Gain/(loss) on sale of real estate owned									75,507	41,272	33,180
Net (income)/loss attributable to noncontrolling interests									(1,722)	(1,548)	(1,444)
Net income/(loss) attributable to UDR, Inc.	85,880	$ 27,695	$ 24,761	$ 91,427	61,065	$ 20,736	$ 10,849	$ 13,657	229,763	106,307	77,818
Reportable apartment home segment assets:
Total segment assets	3,811,985				3,816,956				3,811,985	3,816,956
Total real estate owned, net of accumulated depreciation	2,153,824				2,273,304				2,153,824	2,273,304
Reconciling items:
Cash and cash equivalents	125				293				125	293	756	3,103
Restricted cash	13,563				12,579				13,563	12,579	11,694	$ 11,344
Investment in and advances to unconsolidated joint ventures, net	103,026				76,907				103,026	76,907
Other assets	34,052				32,490				34,052	32,490
Total consolidated assets	2,304,590				2,395,573				2,304,590	2,395,573
United Dominion Reality L.P. | Same Communities
Reportable Segments
Capital expenditures and development									41,000	41,800	41,500
United Dominion Reality L.P. | 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									246,047	235,022	223,539
Reportable apartment home segment NOI									187,664	177,229	168,762
Reportable apartment home segment assets:
Total segment assets	1,981,007				1,955,962				1,981,007	1,955,962
United Dominion Reality L.P. | 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									60,389	59,006	57,563
Reportable apartment home segment NOI									41,642	40,292	38,711
Reportable apartment home segment assets:
Total segment assets	663,083				655,850				663,083	655,850
United Dominion Reality L.P. | 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									54,749	54,530	53,036
Reportable apartment home segment NOI									39,456	40,524	40,704
Reportable apartment home segment assets:
Total segment assets	681,953				677,767				681,953	677,767
United Dominion Reality L.P. | 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									51,896	49,586	47,792
Reportable apartment home segment NOI									35,948	34,182	32,519
Reportable apartment home segment assets:
Total segment assets	340,722				334,811				340,722	334,811
United Dominion Reality L.P. | Non-Mature communities/Other
Reportable Segments
Capital expenditures and development									900	1,800	2,600
Summary of rental income and NOI for UDRs reportable segments and reconciliation of NOI to loss from continuing operations
Lease Revenue									18,839	21,233	22,485
Reportable apartment home segment NOI									12,670	14,614	$ 16,425
Reportable apartment home segment assets:
Total segment assets	$ 145,220				$ 192,566				$ 145,220	$ 192,566
Minimum
Reportable Segments
Community Threshold, Percent Occupancy Threshold									90%
Time to maintain percent occupancy to be considered a community									3 months
Minimum | United Dominion Reality L.P.
Reportable Segments
Community Threshold, Percent Occupancy Threshold									90%
Time to maintain percent occupancy to be considered a community									3 months
Taxable REIT Subsidiaries
Reportable Segments
Management fee (as a percent)									2.75%