The percentage of debt instruments tendered.

No definition available.

Name:	udr_DebtInstrumentsTenderedPercent
Namespace Prefix:	udr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The value of debt instruments tendered.

+ References

No definition available.

+ Details

Name:	udr_DebtTenderedValue
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the debt price as a percentage of the principal amount at which the debt instrument is issued.

+ References

No definition available.

+ Details

Name:	udr_LongTermDebtPriceAsPercentageOfPrincipalAmount
Namespace Prefix:	udr_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Secured debt including debt on real estate held for sale.

+ References

No definition available.

+ Details

Name:	udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of tender offer consideration per each $1,000 principal amount.

+ References

No definition available.

+ Details

Name:	udr_TenderOfferAmountPerPrincipalAmount
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unsecured short-term debt instrument issued by corporations which are highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

No definition available.

+ Details

Name:	us-gaap_CommercialPaperAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

Name:	us-gaap_ExtinguishmentOfDebtAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12069-110248

+ Details

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term unsecured obligations issued by corporations and other borrowers to investors (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20,22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongtermCommercialPaperCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfDebtExtinguishmentCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

+ Details

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=udr_FixedRateDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_MortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_TaxExemptNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=udr_VariableRateDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_TermLoanFacilityDueSeptember2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_A3.75MTNDueJuly2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_TwoPointOneZeroPercentMediumTermNoteDueAugust12032Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_SecuredDebtAt4.64DueIn2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_A4.00MediumTermNoteDueOctober2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_A2.95MediumTermNoteDueSeptember2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_A3.50MediumTermNoteDueJuly2027Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_A3.50MediumTermNotesDueJanuary2028Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_SeniorUnsecuredMediumTermNotes3.2PercentDueJanuary2030Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_MediumTermNotesDueAugust2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_ThreePointOneZeroPercentSeniorUnsecuredNotesDue2034Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=udr_UnitedDominionRealityLPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_FinancialGuaranteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=udr_UdrBankCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=udr_OperatingPartnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_UnsecuredCommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_ThreePointSevenTermNotesDueOctober2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_TermNote4.40PercentageDueJanuary2029Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=udr_CashTenderOfferMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

DEBT, NET (UNITED DOMINION REALTY, L.P.) - Additional Information (Details)			1 Months Ended
	Jul. 21, 2020 USD ($)	Jul. 14, 2020 USD ($)	Feb. 29, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Oct. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)
Fixed and variable rate debt
Long-term commercial paper				$ 500,000,000.0
Borrowings outstanding				2,900,000		$ 2,900,000
Commercial Paper
Fixed and variable rate debt
Commercial paper program				$ 185,000,000		$ 300,000,000
Interest rate at the end of the period				0.40%		2.00%
Credit facilities \| Fixed Rate Debt
Fixed and variable rate debt
Principal outstanding				$ 202,254,000		$ 204,590,000
Mortgages Note Payable \| Fixed Rate Debt
Fixed and variable rate debt
Principal outstanding				855,585,000		884,869,000
Tax-exempt secured notes payable \| Variable Rate Debt
Fixed and variable rate debt
Principal outstanding				27,000,000		27,000,000
Term Loan due September 2023
Fixed and variable rate debt
Senior Notes				35,000,000		35,000,000
3.75% Medium-Term Notes Due July 2024
Fixed and variable rate debt
Senior Notes				299,583,000		299,530,000
2.10% Medium Term Note Due August 1, 2032
Fixed and variable rate debt
Interest rate	2.10%
Debt	$ 400,000,000.0
Price as percentage of principal amount	99.894
4.64% Secured Debt Due in 2023
Fixed and variable rate debt
Interest rate	4.64%
Repayment of debt	$ 245,800,000
4.00% Medium-Term Note due October 2025
Fixed and variable rate debt
Senior Notes				299,638,000		299,604,000
2.95% Medium-Term Note due September 2026
Fixed and variable rate debt
Senior Notes				300,000,000		300,000,000
3.50 Medium-Term Note due July 2027
Fixed and variable rate debt
Senior Notes				299,506,000		299,471,000
3.50% Medium-Term Notes Due January 2028
Fixed and variable rate debt
Senior Notes				299,106,000		299,046,000
3.20% Medium-Term Notes due January 2030
Fixed and variable rate debt
Guarantor borrowing capacity				600,000,000
Interest rate			3.20%				3.20%	3.20%
Senior Notes			$ 600,000,000.0	613,099,000		402,281,000
Debt			$ 200,000,000.0				$ 100,000,000.0	$ 300,000,000.0
Price as percentage of principal amount			105.660
Medium-Term Notes Due August 2031
Fixed and variable rate debt
Guarantor borrowing capacity				400,000,000
Debt				150,000,000.0
3.10% senior unsecured notes due 2034
Fixed and variable rate debt
Guarantor borrowing capacity				300,000,000
United Dominion Realty L.P. \| Financial Guarantee
Fixed and variable rate debt
Guarantor borrowing capacity				1,100,000,000
United Dominion Realty L.P. \| Unsecured Commercial Bank Credit Facility
Fixed and variable rate debt
Long-term commercial paper				500,000,000
United Dominion Realty L.P. \| Mortgages Note Payable
Fixed and variable rate debt
Principal outstanding				$ 72,500,000
Interest rate				3.10%
United Dominion Realty L.P. \| Mortgages Note Payable \| Fixed Rate Debt
Fixed and variable rate debt
Principal outstanding				$ 72,500,000		72,500,000
United Dominion Realty L.P. \| Mortgages Note Payable \| Variable Rate Debt \| Operating Partnership
Fixed and variable rate debt
Principal outstanding				$ 27,000,000.0
Interest rate at the end of the period				0.85%
United Dominion Realty L.P. \| Tax-exempt secured notes payable \| Variable Rate Debt
Fixed and variable rate debt
Principal outstanding				$ 27,000,000		27,000,000
United Dominion Realty L.P. \| Unsecured Commercial Paper
Fixed and variable rate debt
Borrowings outstanding				185,000,000.0		$ 300,000,000.0
United Dominion Realty L.P. \| 3.70% Term Notes Due October 2020
Fixed and variable rate debt
Guarantor borrowing capacity				300,000,000
United Dominion Realty L.P. \| Term Loan due September 2023
Fixed and variable rate debt
Guarantor borrowing capacity				350,000,000
United Dominion Realty L.P. \| 3.75% Medium-Term Notes Due July 2024
Fixed and variable rate debt
Guarantor borrowing capacity					$ 300,000,000
United Dominion Realty L.P. \| 2.10% Medium Term Note Due August 1, 2032
Fixed and variable rate debt
Guarantor borrowing capacity	$ 400,000,000.0
Interest rate	2.10%
Price as percentage of principal amount	99.894
United Dominion Realty L.P. \| 4.64% Secured Debt Due in 2023
Fixed and variable rate debt
Interest rate	4.64%
Repayment of debt	$ 245,800,000
United Dominion Realty L.P. \| 4.00% Medium-Term Note due October 2025
Fixed and variable rate debt
Guarantor borrowing capacity				300,000,000
United Dominion Realty L.P. \| 2.95% Medium-Term Note due September 2026
Fixed and variable rate debt
Guarantor borrowing capacity				300,000,000
United Dominion Realty L.P. \| 3.50 Medium-Term Note due July 2027
Fixed and variable rate debt
Guarantor borrowing capacity				300,000,000
United Dominion Realty L.P. \| Medium-Term note due January 2029
Fixed and variable rate debt
Guarantor borrowing capacity				300,000,000
Credit facilities
Fixed and variable rate debt
Principal outstanding				$ 202,300,000
Cash Tender Offer \| 3.75% Medium-Term Notes Due July 2024
Fixed and variable rate debt
Principal outstanding		$ 300,000,000.0
Interest rate		3.75%
Tendered value		$ 116,900,000
Tendered percentage		39.00%
Tender offer consideration per each $1,000		$ 1,101.92
Make-whole amount		24,000,000.0
Cash Tender Offer \| United Dominion Realty L.P. \| 3.75% Medium-Term Notes Due July 2024
Fixed and variable rate debt
Principal outstanding		$ 300,000,000.0
Interest rate		3.75%
Tendered value		$ 116,900,000
Tendered percentage		39.00%
Tender offer consideration per each $1,000		$ 1,101.92
Make-whole amount		$ 24,000,000.0