XML 92 R99.htm IDEA: XBRL DOCUMENT v2.4.1.9
Fair Value of Derivatives and Financial Instruments (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financing Receivable, Net $ 14,369us-gaap_NotesReceivableNet $ 83,033us-gaap_NotesReceivableNet  
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Derivative Asset 88us-gaap_DerivativeAssets 0us-gaap_DerivativeAssets  
Derivative Asset Designated as Hedging Instrument, Fair Value 88us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral 0us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral  
Derivative Liability   4,965us-gaap_DerivativeLiabilities  
Derivatives - Interest rate contracts 10,368us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral 4,965us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral  
Secured debt instruments - variable rate      
Long-term Line of Credit 1,900us-gaap_LineOfCredit 2,200us-gaap_LineOfCredit  
Unsecured debt instruments      
Redeemable Noncontrolling Interest, Equity, Carrying Amount   217,597us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount 223,418us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount
Redeemable non-controlling interests in operating partnership 282,480us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount 217,597us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount  
Carrying Amount | Fair Value, Measurements, Recurring      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financing Receivable, Net 14,369us-gaap_NotesReceivableNet
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= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
83,033us-gaap_NotesReceivableNet
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Total assets 14,457us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
83,033us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Unsecured debt instruments      
Total liabilities 3,593,473us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
3,528,668us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Redeemable Noncontrolling Interest, Equity, Carrying Amount 282,480us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Redeemable non-controlling interests in operating partnership   217,597us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[1]  
Carrying Amount | Interest rate contracts | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Derivative Liability 10,368us-gaap_DerivativeLiabilities
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= us-gaap_InterestRateContractMember
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= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivatives - Interest rate contracts   4,965us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
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= us-gaap_InterestRateContractMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[2]  
Carrying Amount | Mortgages [Member] | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate   445,706udr_FixedRateSecuredDebtInstrumentsFairValue
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/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Secured debt instruments - variable rate      
Secured debt instruments - variable rate   63,595udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Carrying Amount | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring      
Secured debt instruments - variable rate      
Secured debt instruments - variable rate   94,700udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= udr_TaxExemptNotesPayableMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Carrying Amount | Fannie Mae credit facilities | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate   626,667udr_FixedRateSecuredDebtInstrumentsFairValue
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= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Secured debt instruments - variable rate      
Secured debt instruments - variable rate   211,409udr_VariableRateSecuredDebtInstrumentsFairValue
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= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Carrying Amount | Senior unsecured notes | Fair Value, Measurements, Recurring      
Unsecured debt instruments      
Unsecured debt instruments 2,069,076udr_UnsecuredDebtInstrumentsFairValue
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/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
2,081,626udr_UnsecuredDebtInstrumentsFairValue
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= us-gaap_SeniorNotesMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Fair Value | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Notes receivable 14,808us-gaap_NotesReceivableFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
83,833us-gaap_NotesReceivableFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Total assets 14,896us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
83,833us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Unsecured debt instruments      
Total liabilities 3,721,512us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
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3,651,141us-gaap_LiabilitiesFairValueDisclosure
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= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Redeemable non-controlling interests in operating partnership 282,480us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[1] 217,597us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[1]  
Fair Value | Interest rate contracts | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Derivative Asset Designated as Hedging Instrument, Fair Value 88us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral
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= us-gaap_FairValueMeasurementsRecurringMember
   
Derivatives - Interest rate contracts 10,368us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
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[1] 4,965us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
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= us-gaap_FairValueMeasurementsRecurringMember
[2]  
Fair Value | Mortgages [Member] | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate 415,663udr_FixedRateSecuredDebtInstrumentsFairValue
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/ us-gaap_FairValueByMeasurementBasisAxis
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= us-gaap_FairValueMeasurementsRecurringMember
[2] 466,375udr_FixedRateSecuredDebtInstrumentsFairValue
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= us-gaap_EstimateOfFairValueFairValueDisclosureMember
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= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 31,337udr_VariableRateSecuredDebtInstrumentsFairValue
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/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
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= us-gaap_FairValueMeasurementsRecurringMember
[2] 63,595udr_VariableRateSecuredDebtInstrumentsFairValue
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= us-gaap_EstimateOfFairValueFairValueDisclosureMember
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= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Fair Value | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring      
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 94,700udr_VariableRateSecuredDebtInstrumentsFairValue
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/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[2] 94,700udr_VariableRateSecuredDebtInstrumentsFairValue
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= us-gaap_EstimateOfFairValueFairValueDisclosureMember
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= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Fair Value | Fannie Mae credit facilities | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate 606,623udr_FixedRateSecuredDebtInstrumentsFairValue
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= us-gaap_FairValueMeasurementsRecurringMember
[2] 661,094udr_FixedRateSecuredDebtInstrumentsFairValue
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= us-gaap_EstimateOfFairValueFairValueDisclosureMember
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= us-gaap_FairValueMeasurementsRecurringMember
[3]  
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 266,196udr_VariableRateSecuredDebtInstrumentsFairValue
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/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
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= us-gaap_FairValueMeasurementsRecurringMember
[2] 211,409udr_VariableRateSecuredDebtInstrumentsFairValue
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= us-gaap_EstimateOfFairValueFairValueDisclosureMember
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[3]  
Fair Value | Senior unsecured notes | Fair Value, Measurements, Recurring      
Unsecured debt instruments      
Unsecured debt instruments 2,144,125udr_UnsecuredDebtInstrumentsFairValue
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[3] 2,149,003udr_UnsecuredDebtInstrumentsFairValue
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[3]  
Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Notes receivable 0us-gaap_NotesReceivableFairValueDisclosure
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0us-gaap_NotesReceivableFairValueDisclosure
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Total assets 0us-gaap_AssetsFairValueDisclosure
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0us-gaap_AssetsFairValueDisclosure
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Unsecured debt instruments      
Total liabilities 0us-gaap_LiabilitiesFairValueDisclosure
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0us-gaap_LiabilitiesFairValueDisclosure
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Redeemable non-controlling interests in operating partnership 0us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
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0us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
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Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Interest rate contracts | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Derivative Asset Designated as Hedging Instrument, Fair Value 0us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral
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Derivatives - Interest rate contracts 0us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
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Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Mortgages [Member] | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate 0udr_FixedRateSecuredDebtInstrumentsFairValue
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Secured debt instruments - variable rate      
Secured debt instruments - variable rate 0udr_VariableRateSecuredDebtInstrumentsFairValue
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Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring      
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 0udr_VariableRateSecuredDebtInstrumentsFairValue
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Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate 0udr_FixedRateSecuredDebtInstrumentsFairValue
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= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 0udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Commercial bank | Fair Value, Measurements, Recurring      
Unsecured debt instruments      
Unsecured debt instruments 0udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= udr_CommercialBankMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value | Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Senior unsecured notes | Fair Value, Measurements, Recurring      
Unsecured debt instruments      
Unsecured debt instruments 0udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_SeniorNotesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_SeniorNotesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Notes receivable 0us-gaap_NotesReceivableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_NotesReceivableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Total assets 88us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Unsecured debt instruments      
Total liabilities 10,368us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
4,965us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Redeemable non-controlling interests in operating partnership 282,480us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
[1] 217,597us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Other Observable Inputs (Level 2) | Interest rate contracts | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Derivative Asset Designated as Hedging Instrument, Fair Value 88us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InterestRateContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivatives - Interest rate contracts 10,368us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InterestRateContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value | Significant Other Observable Inputs (Level 2) | Mortgages [Member] | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate 0udr_FixedRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0udr_FixedRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 0udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Other Observable Inputs (Level 2) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring      
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 0udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= udr_TaxExemptNotesPayableMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= udr_TaxExemptNotesPayableMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Other Observable Inputs (Level 2) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate 0udr_FixedRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0udr_FixedRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 0udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Other Observable Inputs (Level 2) | Commercial bank | Fair Value, Measurements, Recurring      
Unsecured debt instruments      
Unsecured debt instruments 0udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= udr_CommercialBankMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value | Significant Other Observable Inputs (Level 2) | Senior unsecured notes | Fair Value, Measurements, Recurring      
Unsecured debt instruments      
Unsecured debt instruments 0udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_SeniorNotesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_SeniorNotesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Notes receivable 14,808us-gaap_NotesReceivableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
83,833us-gaap_NotesReceivableFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Total assets 14,808us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
83,833us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Unsecured debt instruments      
Total liabilities 3,711,144us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
3,646,176us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Redeemable non-controlling interests in operating partnership 0us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_RedeemableNoncontrollingInterestEquityCommonCarryingAmount
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Unobservable Inputs (Level 3) | Interest rate contracts | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Derivative Asset Designated as Hedging Instrument, Fair Value 0us-gaap_DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InterestRateContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Derivatives - Interest rate contracts 0us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InterestRateContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
0us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_InterestRateContractMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Unobservable Inputs (Level 3) | Mortgages [Member] | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate 415,663udr_FixedRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
466,375udr_FixedRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 31,337udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
63,595udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Unobservable Inputs (Level 3) | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring      
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 94,700udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= udr_TaxExemptNotesPayableMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
94,700udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= udr_TaxExemptNotesPayableMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Unobservable Inputs (Level 3) | Fannie Mae credit facilities | Fair Value, Measurements, Recurring      
Secured debt instruments - fixed rate      
Secured debt instruments - fixed rate 606,623udr_FixedRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
661,094udr_FixedRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Secured debt instruments - variable rate      
Secured debt instruments - variable rate 266,196udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
211,409udr_VariableRateSecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fair Value | Significant Unobservable Inputs (Level 3) | Commercial bank | Fair Value, Measurements, Recurring      
Unsecured debt instruments      
Unsecured debt instruments 152,500udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= udr_CommercialBankMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
   
Fair Value | Significant Unobservable Inputs (Level 3) | Senior unsecured notes | Fair Value, Measurements, Recurring      
Unsecured debt instruments      
Unsecured debt instruments 2,144,125udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_SeniorNotesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
2,149,003udr_UnsecuredDebtInstrumentsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_SeniorNotesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
 
Fixed Rate Debt      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale 969,296udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
1,072,373udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
 
Variable Rate Debt      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale 392,233udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
369,704udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
 
Unsecured Revolving Credit Facility due October 2015      
Secured debt instruments - variable rate      
Long-term Line of Credit 152,500us-gaap_LineOfCredit
/ us-gaap_LongtermDebtTypeAxis
= udr_UnsecuredRevolvingCreditFacilityDueOctoberTwoThousandFifteenMember
0us-gaap_LineOfCredit
/ us-gaap_LongtermDebtTypeAxis
= udr_UnsecuredRevolvingCreditFacilityDueOctoberTwoThousandFifteenMember
 
Tax-exempt secured notes payable | Variable Rate Debt      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale   94,700udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= udr_TaxExemptNotesPayableMember
 
Tax-exempt secured notes payable | Variable Rate Debt | Carrying Amount | Tax-exempt secured notes payable | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale 94,700udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_FairValueByAssetClassAxis
= udr_TaxExemptNotesPayableMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_LongtermDebtTypeAxis
= udr_TaxExemptNotesPayableMember
   
Line of Credit [Member] | Fixed Rate Debt      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale   626,667udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
 
Line of Credit [Member] | Fixed Rate Debt | Carrying Amount | Fannie Mae credit facilities | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale 568,086udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
   
Line of Credit [Member] | Variable Rate Debt      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale   211,409udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
 
Line of Credit [Member] | Variable Rate Debt | Carrying Amount | Fannie Mae credit facilities | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale 266,196udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_LineOfCreditMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
   
Mortgages [Member] | Fixed Rate Debt      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale   445,706udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
 
Mortgages [Member] | Fixed Rate Debt | Carrying Amount | Mortgages [Member] | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale 401,210udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
   
Mortgages [Member] | Variable Rate Debt      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale   63,595udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
 
Mortgages [Member] | Variable Rate Debt | Carrying Amount | Mortgages [Member] | Fair Value, Measurements, Recurring      
Estimated fair values of the financial instruments either recorded or disclosed on a recurring basis      
Secured Debt Including Debt on Real Estate Held for Sale $ 31,337udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgagesMember
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember
   
[1] See Note 6, Secured Debt and Unsecured Debt.
[2] See Note 2, Significant Accounting Policies.
[3] See Note 13, Derivatives and Hedging Activity.