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

Extension period of option on loan

+ References

No definition available.

+ Details

Name:	udr_ExtensionPeriodOfOptionOnLoan
Namespace Prefix:	udr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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

Number of Extensions of loan

+ References

No definition available.

+ Details

Name:	udr_NumberOfExtensionsOfLoan
Namespace Prefix:	udr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Portion of Medium Term Note subject to Interest Rate Swaps

+ References

No definition available.

+ Details

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

- Definition

Secured Debt, Encumbers Real Estate Owned, Amount.

+ References

No definition available.

+ Details

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

- Definition

Secured Debt, Encumbers Real Estate Owned, Percent.

+ References

No definition available.

+ Details

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

- 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 secured debt refinanced during the reporting period.

+ References

No definition available.

+ Details

Name:	udr_SecuredDebtRefinancedAmount
Namespace Prefix:	udr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Secured debt.

+ References

No definition available.

+ Details

Name:	udr_SecuredDebtTextualAbstract
Namespace Prefix:	udr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Secured Debt, Unencumbered Real Estate Owned, Amount.

+ References

No definition available.

+ Details

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

- Definition

Secured Debt, Unencumbered Real Estate Owned, Percent.

+ References

No definition available.

+ Details

Name:	udr_SecuredDebtUnencumberedRealEstateOwnedPercent
Namespace Prefix:	udr_
Data Type:	num:percentItemType
Balance Type:	na
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

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

+ Details

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

- Definition

Amount of amortization expense attributable to debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(8))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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=119993939&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

The average effective interest rate during the reporting period.

+ 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=119993939&loc=d3e28551-108399

Reference 2: 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(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

Reference 2: 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=119993939&loc=d3e28551-108399

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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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

Amount, after accumulated amortization, of debt premium.

+ References

Reference 1: 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

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

+ Details

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

- 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

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12317-112629

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

+ Details

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

- 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=120391452&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=120398452&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=120400017&loc=d3e572229-122910

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).

+ References

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Weighted average interest rate of long-term debt outstanding calculated over time.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtWeightedAverageInterestRateOverTime
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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=121586364&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

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(a))
-URI http://asc.fasb.org/extlink&oid=120400017&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=120398452&loc=d3e534808-122878

+ Details

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

- Details

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

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_UnsecuredWorkingCapitalCreditFacilityDueJanuary2021Member
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_TypeOfArrangementAxis=udr_CashTenderOfferMember
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_Notes2.10DueIn2032And4.64DueIn2023Member
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_DebtInstrumentAxis=udr_FixedRateDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_MortgageNotePayableMaturesOnNovember2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_MortgageNotePayableMaturesOn2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
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_A4.00MediumTermNoteDueOctober2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_FourPointFourZeroPercentMediumTermNoteDueJanuaryTwoThousandTwentyNineMember
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_SeniorUnsecuredMediumTermNotes3.2PercentDueJanuary2030Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_MediumTerm3.00PercentageNoteDueAugust2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_ThreePointTwoFourPercentDueOnTwoThousandThirtyMember
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:	srt_RangeAxis=srt_WeightedAverageMember
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:	us-gaap_LineOfCreditFacilityAxis=udr_UdrBankCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=udr_UnsecuredRevolvingCreditFacilityDueTwoThousandTwentyThreeMember
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_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_MortgagesMember
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_LongtermDebtTypeAxis=udr_UnsecuredCommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SECURED AND UNSECURED DEBT, NET - Debt Covenants (Details)	1 Months Ended		3 Months Ended		9 Months Ended
	Jul. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	Sep. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Oct. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)
Fixed and variable rate debt
Amortization of financing costs			$ 1,100,000	$ 1,100,000	$ 3,200,000	$ 3,100,000
Secured Debt
Secured debt amount which encumbers real estate owned based upon book value			$ 1,500,000,000		$ 1,500,000,000
Percentage of secured debt which encumbers real estate owned based upon book value			11.60%		11.60%
Secured debt amount of real estate owned which is unencumbered			$ 11,400,000,000		$ 11,400,000,000
Percentage of secured debt of real estate owned which is unencumbered			88.40%		88.40%
Interest rate at end of the period					3.01%
Extinguishment of debt costs					$ 35,495,000	6,283,000
Borrowings outstanding at end of period			$ 2,900,000		2,900,000		$ 2,900,000
Unamortized net premium			16,200,000		16,200,000		35,300,000
Prepayment costs					$ (24,540,000)	(6,283,000)
Weighted Average Interest Rate					3.01%
Unsecured Debt
Secured Debt
Interest rate at end of the period					3.08%
Credit facility interest rate					90
Basis points added to to variable rate					90.00%
Weighted Average Interest Rate					3.08%
Unsecured Debt \| Maximum
Secured Debt
Basis points added to to variable rate					165.00%
Unsecured Debt \| Minimum
Secured Debt
Basis points added to to variable rate					80.00%
Unsecured Working Capital Credit Facility
Secured Debt
Credit facilities with aggregate commitment			75,000,000		$ 75,000,000		75,000,000
Interest rate at end of the period					0.97%
Credit facility interest rate					82.5
Borrowings outstanding at end of period			22,086,000		$ 22,086,000		16,583,000
Weighted Average Interest Rate					0.97%
Unsecured Working Capital Credit Facility \| Maximum
Secured Debt
Basis points added to to variable rate					145.00%
Unsecured Working Capital Credit Facility \| Minimum
Secured Debt
Basis points added to to variable rate					75.00%
3.75% Medium-Term Notes Due July 2024
Secured Debt
Interest rate at end of the period					3.69%
Extinguishment of debt costs			12,800,000		$ 12,800,000
Portion of medium term note subject to interest rate swaps			100,000,000.0		$ 100,000,000.0
Long-term Debt, Weighted Average Interest Rate					3.69%
Senior Notes			182,867,000		$ 182,867,000		299,530,000
Weighted Average Interest Rate					3.69%
3.75% Medium-Term Notes Due July 2024 \| Cash Tender Offer
Secured 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
2.10% Medium Term Note Due August 1, 2032
Secured Debt
Interest rate at end of the period					2.10%
Interest rate	2.10%
Senior Notes			399,583,000		$ 399,583,000
Debt	$ 400,000,000.0
Price as percentage of principal amount	99.894
Weighted Average Interest Rate					2.10%
4.64% Secured Debt Due in 2023
Secured Debt
Interest rate	4.64%
Repayment of debt	$ 245,800,000
2.10% Due in 2032 and 4.64% due in 2023 Notes
Secured Debt
Extinguishment of debt costs	24,000,000.0
Mortgages Note Payable
Secured Debt
Repayment of debt			43,900,000
Mortgages Note Payable \| Fixed Rate Debt
Secured Debt
Principal outstanding			892,291,000		$ 892,291,000		884,869,000
Interest rate at end of the period					3.36%
Extinguishment of debt costs			2,200,000		$ 2,200,000
Weighted Average Interest Rate					3.36%
Mortgage Note Payable Matures on November 2020 \| Fixed Rate Debt
Secured Debt
Refinanced debt	$ 79,300,000
Interest rate	4.35%
Extinguishment of debt costs	$ 500,000
Mortgage Note Payable Matures on 2031 \| Fixed Rate Debt
Secured Debt
Principal outstanding	$ 160,900,000
Interest rate	2.62%
Debt Assumed As Part of Acquisition
Secured Debt
Amortization of debt discount (Premium)			14,000,000.0	$ 600,000	$ 19,100,000	$ 1,700,000
Tax-exempt secured notes payable \| Variable Rate Debt
Secured Debt
Principal outstanding			27,000,000		$ 27,000,000		27,000,000
Interest rate at end of the period					0.77%
Weighted Average Interest Rate					0.77%
Credit facilities \| Fixed Rate Debt
Secured Debt
Principal outstanding							204,590,000
Extinguishment of debt costs			9,000,000.0		$ 9,000,000.0
Repayment of debt			$ 201,900,000
Tax-exempt secured notes payable \| Variable Rate Debt
Secured Debt
Notes payable maximum interest rates range			0.77%		0.77%
Revolving Credit Facility
Secured Debt
Basis points added to to variable rate					82.50%
Commitment fee					15.00%
Revolving Credit Facility \| Maximum
Secured Debt
Basis points added to to variable rate					145.00%
Commitment fee					30.00%
Revolving Credit Facility \| Minimum
Secured Debt
Basis points added to to variable rate					75.00%
Commitment fee					10.00%
Term Loan due September 2023
Secured Debt
Interest rate at end of the period					1.06%
Long-term Debt, Weighted Average Interest Rate					2.55%
Senior Notes			$ 35,000,000		$ 35,000,000		35,000,000
Weighted Average Interest Rate					1.06%
Term Loan due September 2023 \| Fixed Rate Debt
Secured Debt
Interest rate at end of the period					2.55%
Senior Notes			315,000,000		$ 315,000,000		315,000,000
Weighted Average Interest Rate					2.55%
4.00% Medium-Term Note due October 2025
Secured Debt
Interest rate at end of the period					4.53%
Portion of medium term note subject to interest rate swaps			200,000,000.0		$ 200,000,000.0
Senior Notes			299,656,000		$ 299,656,000		299,604,000
Weighted Average Interest Rate					4.53%
4.40% Medium-Term Notes due January 2029
Secured Debt
Interest rate at end of the period					4.27%
Portion of medium term note subject to interest rate swaps			150,000,000.0		$ 150,000,000.0
Long-term Debt, Weighted Average Interest Rate					4.27%
Senior Notes			299,995,000		$ 299,995,000		299,995,000
Weighted Average Interest Rate					4.27%
4.40% Medium-Term Notes due January 2029 \| Cash Tender Offer
Secured Debt
Principal outstanding	$ 300,000,000.0
2.95% Medium-Term Note due September 2026
Secured Debt
Interest rate at end of the period					2.95%
Senior Notes			300,000,000		$ 300,000,000		300,000,000
Weighted Average Interest Rate					2.95%
3.20% Medium-Term Notes due January 2030
Secured Debt
Interest rate at end of the period		3.32%			3.32%
Interest rate		3.20%						3.20%	3.20%
Senior Notes		$ 600,000,000.0	612,756,000		$ 612,756,000		402,281,000
Debt		$ 200,000,000.0						$ 100,000,000.0	$ 300,000,000.0
Price as percentage of principal amount		105.660
Weighted Average Interest Rate		3.32%			3.32%
3.00% Medium-Term Notes due August 2031
Secured Debt
Interest rate at end of the period					3.01%
Senior Notes			398,949,000		$ 398,949,000		398,877,000
Weighted Average Interest Rate					3.01%
3.24% Notes due on 2030
Secured Debt
Debt								$ 100,000,000.0
Medium-Term Notes Due August 2031
Secured Debt
Debt			150,000,000.0		$ 150,000,000.0
Medium-Term Notes Due August 2031 \| Weighted Average
Secured Debt
Interest rate at end of the period					3.01%
Weighted Average Interest Rate					3.01%
3.10% senior unsecured notes due 2034 \| Weighted Average
Secured Debt
Interest rate at end of the period					3.13%
Weighted Average Interest Rate					3.13%
Unsecured Commercial Bank Credit Facility
Secured Debt
Credit facilities with aggregate commitment			2,000,000,000.0		$ 2,000,000,000.0
Unsecured Commercial Bank Credit Facility \| Unsecured Revolving credit facility due 2023
Secured Debt
Credit facilities with aggregate commitment			$ 1,100,000,000		$ 1,100,000,000
Number of Extensions of loan \| loan			2		2
Extension period of option on loan					6 months
Unsecured Commercial Bank Credit Facility \| Revolving Credit Facility
Secured Debt
Credit facilities with aggregate commitment			$ 1,100,000,000		$ 1,100,000,000		1,100,000,000
Unsecured Commercial Bank Credit Facility \| Term Loan due September 2023
Secured Debt
Credit facilities with aggregate commitment			$ 350,000,000.0		$ 350,000,000.0
Credit facilities \| Fair Value, Measurements, Recurring \| Carrying Amount \| Credit facilities \| Fixed Rate Debt
Secured Debt
Principal outstanding							218,490,000
Mortgages Note Payable \| Fixed Rate Debt \| Maximum
Secured Debt
Notes payable maximum interest rates range			4.12%		4.12%
Mortgages Note Payable \| Fixed Rate Debt \| Minimum
Secured Debt
Notes payable maximum interest rates range			2.62%		2.62%
Mortgages Note Payable \| Fair Value, Measurements, Recurring \| Carrying Amount \| Mortgages Note Payable \| Fixed Rate Debt
Secured Debt
Principal outstanding			$ 908,493,000		$ 908,493,000		906,228,000
United Dominion Realty L.P.
Secured Debt
Notes payable maximum interest rates range			3.01%		3.01%
Interest rate at end of the period					2.52%
Weighted Average Interest Rate					2.52%
United Dominion Realty L.P. \| Fixed Rate Debt
Secured Debt
Interest rate at end of the period					3.10%
Weighted Average Interest Rate					3.10%
United Dominion Realty L.P. \| Variable Rate Debt
Secured Debt
Interest rate at end of the period					0.77%
Weighted Average Interest Rate					0.77%
United Dominion Realty L.P. \| Mortgages Note Payable
Secured Debt
Principal outstanding			$ 72,500,000		$ 72,500,000
Interest rate			3.10%		3.10%
United Dominion Realty L.P. \| Mortgages Note Payable \| Fixed Rate Debt
Secured Debt
Principal outstanding			$ 72,500,000		$ 72,500,000		72,500,000
Interest rate at end of the period					3.10%
Weighted Average Interest Rate					3.10%
United Dominion Realty L.P. \| Tax-exempt secured notes payable \| Variable Rate Debt
Secured Debt
Principal outstanding			27,000,000		$ 27,000,000		27,000,000
Interest rate at end of the period					0.77%
Weighted Average Interest Rate					0.77%
United Dominion Realty L.P. \| Unsecured Commercial Paper
Secured Debt
Borrowings outstanding at end of period			$ 230,000,000.0		$ 230,000,000.0		$ 300,000,000.0