CONSOLIDATION AND BASIS OF PRESENTATION (Details)	12 Months Ended
	Dec. 31, 2019 home USD ($) community item shares	Dec. 31, 2018 shares	Dec. 31, 2017 shares	Dec. 31, 2016 shares
Consolidation And Basis Of Presentation
Number of Real Estate Properties | community	148
Number of Markets Operating Within | $	20
Number Of Apartment Homes Owned And Consolidated By Company | home	47,010
Operating Partnership units outstanding related to limited partner	184,064,000	183,637,000	183,351,000	183,279,000
Joint venture, number of completed or to be completed homes in communities | home	5,268
Preferred equity investment,, number of apartment homes | home	2,138
Operating Partnership outstanding units	184,100,000	183,600,000
United Dominion Realty L.P.
Consolidation And Basis Of Presentation
Operating Partnership units outstanding related to limited partner	176,200,000	174,200,000
Percentage of units outstanding in Partnership	95.70%	94.90%
UDR Lighthouse DownREIT L.P.
Consolidation And Basis Of Presentation
General Partners' ownership (as a percent)		53.20%
Operating Partnership outstanding units	13,500,000
Percentage of units outstanding in Partnership	41.70%
UDR Lighthouse DownREIT L.P.
Consolidation And Basis Of Presentation
Operating Partnership outstanding units	32,400,000	13,500,000
Percentage of units outstanding in Partnership		41.60%
Non-affiliated Partners
Consolidation And Basis Of Presentation
Operating Partnership units outstanding related to limited partner	7,900,000
Operating Partnership outstanding units	14,000,000.0	9,400,000
Percentage of units outstanding in Partnership	4.30%	5.10%
Non-affiliated Partners | United Dominion Realty L.P.
Consolidation And Basis Of Presentation
Operating Partnership units outstanding related to limited partner	7,900,000
Operating Partnership outstanding units	7,900,000	9,400,000
Percentage of units outstanding in Partnership	4.30%	5.10%
Non-affiliated Partners | UDR Lighthouse DownREIT L.P.
Consolidation And Basis Of Presentation
Operating Partnership outstanding units		15,200,000
Percentage of units outstanding in Partnership	43.20%	46.80%
UDR, Inc.
Consolidation And Basis Of Presentation
Operating Partnership units outstanding related to limited partner	176,100,000	174,100,000
General Partners' ownership (as a percent)	56.80%
Operating Partnership outstanding units	18,400,000	17,200,000
Percentage of units outstanding in Partnership	95.70%	94.90%
UDR, Inc. | United Dominion Realty L.P.
Consolidation And Basis Of Presentation
Operating Partnership units outstanding related to limited partner	176,100,000	174,100,000
General Partners' ownership (as a percent)	95.70%	94.90%
Operating Partnership outstanding units	176,200,000	174,200,000
Percentage of units outstanding in Partnership	95.70%	94.80%
United Dominion Realty L.P.
Consolidation And Basis Of Presentation
Number of Real Estate Properties | community	52
Number of Markets Operating Within | item	15
Number Of Apartment Homes Owned And Consolidated By Company | home	16,434
Operating Partnership units outstanding related to limited partner	183,952,659	183,525,660
Operating Partnership outstanding units	184,100,000	183,600,000