Extension period of option on loan

No definition available.

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

- Definition

Maximum borrowing capacity the credit facility could be adjusted to per agreement.

+ References

No definition available.

+ Details

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

- Definition

Number of Extensions of loan

+ References

No definition available.

+ Details

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

- Definition

Summary of short-term bank borrowings under UDR's bank credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	udr_
Data Type:	xbrli:stringItemType
Balance Type:	na
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

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

- Definition

Average fixed interest rate related to the group of interest rate derivatives.

+ References

No definition available.

+ Details

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

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

+ Details

Name:	us-gaap_DerivativeNumberOfInstrumentsHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
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=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

Average amount borrowed under the credit facility during the period.

+ References

No definition available.

+ Details

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

- 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

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

The effective interest rate during the reporting period.

+ References

+ Details

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

- Definition

Maximum amount borrowed under the credit facility at any time during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumAmountOutstandingDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

- Details

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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_DebtInstrumentAxis=udr_UnsecuredRevolvingCreditFacilityDueTwoThousandTwentyThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LetterOfCreditMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
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- Details

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- Details

Name:	us-gaap_DebtInstrumentAxis=udr_TermLoanFacilityDueSeptember2023Member
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Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=udr_UnsecuredWorkingCapitalCreditFacilityDueJanuary2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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SECURED AND UNSECURED DEBT, NET - Credit Facilities (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) loan	Dec. 31, 2020 USD ($)	Nov. 30, 2020 instrument
Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	90.00%
Revolving Credit Facility
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	$ 1,100,000
Potential maximum available	$ 2,000,000
Number of Extensions of loan \| loan	2
Extension period of option on loan	6 months
Revolving credit facility due 2023 \| Letter of Credit
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Borrowings outstanding at end of year	$ 2,600	$ 2,800
Revolving credit facility due 2023 \| Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Commitment fee	0.15%
Basis points added to to variable rate	0.825%
Revolving credit facility due 2023 \| Unsecured Debt \| Minimum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Commitment fee	0.10%
Basis points added to to variable rate	0.75%
Revolving credit facility due 2023 \| Unsecured Debt \| Maximum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Commitment fee	0.30%
Basis points added to to variable rate	1.45%
Revolving credit facility due 2023 \| Revolving Credit Facility
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	$ 1,100,000	1,100,000
Weighted average daily borrowings during the year ended		42,186
Maximum daily borrowings during the year ended		$ 375,000
Weighted average interest rate during the year ended		1.40%
Term Loan due September 2023
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	$ 350,000
Term Loan due September 2023 \| Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Number of interest rate swaps \| instrument			3
All-in weighted average interest rate			1.07%
Term Loan due September 2023 \| Unsecured Debt \| Minimum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	0.80%
Term Loan due September 2023 \| Unsecured Debt \| Maximum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	1.65%
Working Capital Credit Facility \| Variable Rate Debt \| Unsecured Debt
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Total revolving credit facility	$ 75,000	$ 75,000
Borrowings outstanding at end of year	27,318	28,024
Weighted average daily borrowings during the year ended	8,839	20,132
Maximum daily borrowings during the year ended	$ 39,503	$ 54,974
Weighted average interest rate during the year ended	0.90%	1.40%
Interest rate at end of the period	0.90%	1.00%
Basis points added to to variable rate	0.825%
Working Capital Credit Facility \| Variable Rate Debt \| Unsecured Debt \| Minimum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	0.75%
Working Capital Credit Facility \| Variable Rate Debt \| Unsecured Debt \| Maximum
Summary of short-term bank borrowings under unsecured commercial bank credit facility
Basis points added to to variable rate	1.45%