JOINT VENTURES AND PARTNERSHIPS - Commitments (Details)		1 Months Ended						12 Months Ended
	Nov. 30, 2019 USD ($) community	Nov. 30, 2019 USD ($) item community	Nov. 30, 2019 USD ($) community	Nov. 30, 2019 USD ($) property community	Nov. 30, 2019 USD ($) community	Aug. 31, 2019 USD ($) home	May 31, 2019 USD ($) home community	Dec. 31, 2019 USD ($) community item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 31, 2019	Apr. 30, 2019 USD ($) home	Jan. 01, 2019 community	Sep. 30, 2018 USD ($) item	Aug. 31, 2018 USD ($) item
Joint Ventures
Real estate owned								$ 12,602,101,000	$ 10,196,159,000
Investment in unconsolidated entities									585,490,000
Time to maintain percent occupancy to be considered a community								3 months
Number of land parcels | property				4
Investment in unconsolidated joint ventures								$ 93,059,000	112,025,000	$ 123,842,000
Gain on consolidation			$ 0
Long-term Debt								4,707,524,000	3,547,787,000
Deferred fees from the sale of properties								9,000,000.0	11,000,000.0
Joint venture management and other fees								$ 14,055,000	$ 11,754,000	$ 11,482,000
Type of revenue								udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember	udr:ManagementAndOtherFeesMember
Management Service
Joint Ventures
Joint venture management and other fees								$ 14,000,000.0	$ 11,600,000	$ 11,400,000
Joint Ventures and Partnerships
Joint Ventures
Liabilities								$ 1,068,200,000	2,174,137,000
UDR/MetLife operating communities
Joint Ventures
UDR's Ownership Interest	50.00%	50.00%	50.00%	50.00%	50.00%
Number of communities acquired | community					10			10
Number of communities under development purchased | community					1			1
Number of land parcels		4		4				4
Total value of joint venture portion that was purchased	$ 1,100,000,000	$ 1,100,000,000	$ 1,100,000,000	$ 1,100,000,000	$ 1,100,000,000
Total value of joint venture that was purchased - UDR's share			564,200,000
Value of Joint Venture Sold	$ 645,800,000	$ 645,800,000	645,800,000	$ 645,800,000	$ 645,800,000
Sale value of joint venture			645,800,000
Sale value of joint venture UDR's share			322,900,000
Payment to acquire real estate			109,200,000
Gain on consolidation			$ 114,900,000					$ 131,500,000
Number of communities sold | community	5	5	5	5	5
Ownership interest (percentage)								50.00%
UDR/MetLife II operating communities
Joint Ventures
Number Of Operating Communities Held Upon Closing Of Transactions | community	7
UDR's Ownership Interest								50.00%
Number of communities acquired | community					15			5
Gain on consolidation								$ 114,900,000
Unconsolidated Joint Venture Vitruvian Park
Joint Ventures
Liabilities									177,099,000
Unconsolidated Joint Venture UDR Met Life I Partnership
Joint Ventures
Liabilities								74,927,000	72,768,000
Unconsolidated Joint Venture UDR MetLife II Partnership
Joint Ventures
Liabilities								434,606,000	1,110,489,000
Unconsolidated Joint Venture Three Washington DC
Joint Ventures
UDR's Ownership Interest						100.00%					30.00%
Payment to acquire real estate						$ 184,000,000.0
Gain on consolidation						$ 0
Number of completed communities | community													3
Number of communities sold | home						292
Acquisition-related costs						$ 2,800,000
Reduction of carrying amount of real estate						$ 23,800,000
Liabilities									167,559,000
Ownership interest (percentage)						100.00%
Unconsolidated Joint Venture Other MetLife
Joint Ventures
Liabilities								464,729,000	464,400,000
Preferred Equity Investment West Coast Development JV
Joint Ventures
Liabilities								$ 93,938,000	181,822,000
Preferred Equity Investment Hillsboro Oregon
Joint Ventures
UDR's Ownership Interest								49.00%
Preferred Equity Investment 1641 Lincoln Santa Monica CA
Joint Ventures
Investment in unconsolidated entities								$ 10,379,000	9,211,000
Income from investments								$ 1,169,000	406,000
Preferred return (as a percent)								12.00%							12.00%
Number of apartment homes															66
Equity Investment															$ 8,800,000
Preferred Equity Investment 1300 Fairmount Philadelphia, PA
Joint Ventures
Investment in unconsolidated entities								$ 51,215,000	8,318,000
Income from investments								3,098,000	159,000
Number of apartment homes | item															471
Equity Investment															$ 51,400,000
Preferred Equity Investment Essex Orlando, FL
Joint Ventures
Investment in unconsolidated entities								14,804,000	9,940,000
Income from investments								$ 1,639,000	$ 258,000
Preferred return (as a percent)								12.50%						12.50%
Number of apartment homes | item														330
Equity Investment														$ 12,900,000
Operating Communities in Arlington, Virginia and Silver Spring, Maryland
Joint Ventures
Number of communities sold | community							2
Number of apartment homes | home							368
Proceeds from sale of real estate							$ 118,300,000
Gain/(loss) on sales of real estate owned, net of tax							$ 10,600,000
Preferred Equity Investment Modera Lake Merritt, Oakland
Joint Ventures
Preferred return (as a percent)												9.00%
Number of apartment homes | home												173
Equity Investment												$ 27,300,000
UDR/KFH joint venture
Joint Ventures
Number of communities sold | community								3
Maximum | Preferred Equity Investment 1300 Fairmount Philadelphia, PA
Joint Ventures
Preferred return (as a percent)															12.00%
Minimum
Joint Ventures
UDR's Ownership Interest								100.00%
Minimum | Preferred Equity Investment 1300 Fairmount Philadelphia, PA
Joint Ventures
Preferred return (as a percent)															8.50%
Market Property LLC | Accounts Payable and Accrued Liabilities
Joint Ventures
Investment in unconsolidated entities								$ 2,800,000