CAPITAL STRUCTURE (UNITED DOMINION REALTY, L.P.) - Ownership Interests (Details) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) class $ / shares shares	Dec. 31, 2019 USD ($) shares
Capital structure
Limited partnership units owned	184,836,000	184,064,000
Redeemable noncontrolling interests in the Operating Partnership \| $	$ 819,133	$ 1,018,665
Number of classes of LTIP Units \| class	2
United Dominion Realty L.P.
Capital structure
General Partnership units outstanding	100,000
Limited partnership units owned	176.2
United Dominion Realty L.P.
Capital structure
General Partnership units outstanding	110,883	110,883
Limited partnership units owned	184,724,677	183,952,659
Required period to be outstanding before unit is redeemable (in years)	1 year
Redeemable noncontrolling interests in the Operating Partnership \| $	$ 314,900	$ 366,400
UDR, Inc.
Capital structure
Limited partnership units owned	176,100,000	176,100,000
Percentage of units	95.30%	95.70%
UDR, Inc. \| United Dominion Realty L.P.
Capital structure
General Partnership units outstanding	176.2
Percentage of units		95.70%
Non-affiliated Partners
Capital structure
Limited partnership units owned	8.6
Percentage of units	4.70%
Non-affiliated Partners \| United Dominion Realty L.P.
Capital structure
Limited partnership units owned	8.6
Percentage of units	4.70%	4.30%
Class A Limited Partner
Capital structure
Cumulative, annual, non-compounded preferred return on Class A Partnership units	8.00%
Value of Class A Partnership units (in dollars per share) \| $ / shares	$ 16.61
Class A Limited Partner \| United Dominion Realty L.P.
Capital structure
Limited partnership units owned	1,900,000	1,900,000
Class A Limited Partner \| UDR, Inc.
Capital structure
Limited partnership units owned	100,000	100,000
Non-affiliated Partners \| United Dominion Realty L.P.
Capital structure
Limited partnership units owned	8,600,000	7,900,000
Percentage of units	4.70%	4.30%
Non-affiliated Partners \| Class A Limited Partner
Capital structure
Limited partnership units owned	1,752,000	1,752,000
LTIP Units One
Capital structure
Vesting period	4 years
Minimum \| LTIP Units
Capital structure
Vesting period	1 year
Period of time LTIP units have been outstanding	2 years
Minimum \| Employee Director \| LTIP Units Two
Capital structure
Vesting period	1 year
Maximum \| LTIP Units
Capital structure
Vesting period	3 years
Maximum \| Employee Director \| LTIP Units Two
Capital structure
Vesting period	3 years

Limited Partners' Capital Account, Required Period To Be Outstanding Before Unit is Redeemable

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Cumulative, annual, non-compounded preferred return percentage of Class A Partnership units.

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Limited Partners' Capital Account, Unit Value1

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Limited Partners Capital Account Units Outstanding Percentage.

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The number of general partner units outstanding.

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The number of limited partner units outstanding.

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As of the reporting date, the carrying amount of noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. The noncontrolling interest holder's ownership (or holders' ownership) may be in the form of common shares (regardless of class), limited partnership units (regardless of class), non-preferential membership interests, or any other form of common equity regardless of investee entity legal form.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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