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Secured Debt and Unsecured Debt (Details Textual) (USD $)
 1 Months Ended 3 Months Ended 12 Months Ended 0 Months Ended
Jun. 30, 2013
Dec. 31, 2014
Dec. 31, 2012
Dec. 31, 2014
Dec. 31, 2013
Sep. 26, 2013
Jun. 26, 2014
Secured Debt (Textual) [Abstract]              
Secured debt amount which encumbers real estate owned based upon book value   $ 2,200,000,000udr_SecuredDebtEncumbersRealEstateOwnedAmount   $ 2,200,000,000udr_SecuredDebtEncumbersRealEstateOwnedAmount       
Percentage of secured debt which encumbers real estate owned based upon book value   26.60%udr_SecuredDebtEncumbersRealEstateOwnedPercent   26.60%udr_SecuredDebtEncumbersRealEstateOwnedPercent       
Secured debt amount of real estate owned which is unencumbered   6,200,000,000udr_SecuredDebtUnencumberedRealEstateOwnedAmount   6,200,000,000udr_SecuredDebtUnencumberedRealEstateOwnedAmount       
Percentage of secured debt of real estate owned which is unencumbered   73.40%udr_SecuredDebtUnencumberedRealEstateOwnedPercent   73.40%udr_SecuredDebtUnencumberedRealEstateOwnedPercent       
Unamortized fair market adjustment   6,700,000us-gaap_DebtInstrumentUnamortizedDiscount   6,700,000us-gaap_DebtInstrumentUnamortizedDiscount 11,800,000us-gaap_DebtInstrumentUnamortizedDiscount    
Weighted Average Interest Rate   3.94%us-gaap_DebtInstrumentInterestRateDuringPeriod          
Long-term Line of Credit   1,900,000us-gaap_LineOfCredit   1,900,000us-gaap_LineOfCredit 2,200,000us-gaap_LineOfCredit    
Line of Credit Facility, Interest Rate Description 100            
Line of Credit Facility, Commitment Fee Description 15            
Fixed Rate Debt              
Secured Debt (Textual) [Abstract]              
Secured Debt Including Debt on Real Estate Held for Sale   969,296,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember		   969,296,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember		 1,072,373,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember		    
Weighted Average Interest Rate   5.26%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember		          
Variable Rate Debt              
Secured Debt (Textual) [Abstract]              
Secured Debt Including Debt on Real Estate Held for Sale   392,233,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember		   392,233,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember		 369,704,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember		    
Weighted Average Interest Rate   1.44%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember		          
Five Point Two Five Percent, Medium Term Notes, Due January 2015 [Member]              
Secured Debt (Textual) [Abstract]              
Unamortized fair market adjustment   6,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		   6,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		 134,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		    
Weighted Average Interest Rate   5.25%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		          
Fixed interest rate   5.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		   5.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		 5.25%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		    
Senior Notes   325,169,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		   325,169,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		 325,041,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointTwoFivePercentMediumTermNotesDueJanuary2015Member		    
3.75 MTN Due July 2024 [Member]              
Secured Debt (Textual) [Abstract]              
Unamortized fair market adjustment   990,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		   990,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		      
Medium-term Notes             300,000,000us-gaap_MediumTermNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member
Weighted Average Interest Rate   3.75%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		          
Fixed interest rate   3.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		   3.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		      
Percentage of Debt Instrument Price   99.652%udr_PercentageofDebtInstrumentPrice
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		   99.652%udr_PercentageofDebtInstrumentPrice
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		      
Senior Notes   299,010,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		   299,010,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		 0us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_A3.75MTNDueJuly2024Member		    
1.67% Term Notes due December 2016              
Secured Debt (Textual) [Abstract]              
Weighted Average Interest Rate   1.31%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= udr_Onepointsixseventermnotesduedecember2016Member		          
Fixed interest rate   1.31%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_Onepointsixseventermnotesduedecember2016Member		   1.31%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_Onepointsixseventermnotesduedecember2016Member		 1.65%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_Onepointsixseventermnotesduedecember2016Member		    
Debt Instrument, Maturity Date     Jun. 01, 2018        
Senior Notes   35,000,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_Onepointsixseventermnotesduedecember2016Member		   35,000,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_Onepointsixseventermnotesduedecember2016Member		 35,000,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_Onepointsixseventermnotesduedecember2016Member		    
Mortgages [Member] | Fixed Rate Debt              
Secured Debt (Textual) [Abstract]              
Debt instrument, maturity date range, start       Dec. 09, 2015      
Debt instrument, maturity date range, end       May 01, 2019      
Notes payable minimum interest rates range       3.43%us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMinimum
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		      
Notes payable maximum interest rates range       5.94%us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMaximum
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		      
Secured Debt Including Debt on Real Estate Held for Sale         445,706,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		    
Weighted Average Interest Rate   5.46%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		          
Mortgages [Member] | Variable Rate Debt              
Secured Debt (Textual) [Abstract]              
Secured Debt Including Debt on Real Estate Held for Sale         63,595,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		    
Weighted Average Interest Rate   1.94%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_MortgagesMember		          
Debt Assumed As Part of Acquisition [Member]              
Secured Debt (Textual) [Abstract]              
Amortization of Debt Discount (Premium)     4,900,000us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_LongtermDebtTypeAxis
= udr_DebtAssumedAsPartOfAcquisitionMember		 5,100,000us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_LongtermDebtTypeAxis
= udr_DebtAssumedAsPartOfAcquisitionMember		 5,100,000us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_LongtermDebtTypeAxis
= udr_DebtAssumedAsPartOfAcquisitionMember		    
Fannie Mae credit facilities | Fixed Rate Debt              
Secured Debt (Textual) [Abstract]              
Debt instrument, maturity date range, start       May 01, 2017      
Debt instrument, maturity date range, end       Jul. 01, 2023      
Number of secured credit facilities       3udr_NumberOfSecuredCreditFacilities
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		      
Credit facilities with aggregate commitment   834,300,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		   834,300,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		      
Secured Debt Including Debt on Real Estate Held for Sale         626,667,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		    
Debt, Weighted Average Interest Rate   5.12%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		   5.12%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_DebtInstrumentAxis
= udr_FixedRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		      
Fannie Mae credit facilities | Variable Rate Debt              
Secured Debt (Textual) [Abstract]              
Secured Debt Including Debt on Real Estate Held for Sale         211,409,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		    
Interest rate at the end of the period   1.60%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		   1.60%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember		      
Tax-exempt secured notes payable | Variable Rate Debt              
Secured Debt (Textual) [Abstract]              
Debt instrument, maturity date range, start   Aug. 01, 2019          
Debt instrument, maturity date range, end   Mar. 20, 2032          
Notes payable minimum interest rates range       0.78%us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMinimum
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= udr_TaxExemptSecuredNotesPayableMember		      
Notes payable maximum interest rates range       0.93%us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMaximum
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_LongtermDebtTypeAxis
= udr_TaxExemptSecuredNotesPayableMember		      
Unsecured Revolving Credit Facility due October 2015              
Secured Debt (Textual) [Abstract]              
Weighted Average Interest Rate   1.09%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= udr_UnsecuredRevolvingCreditFacilityDueOctoberTwoThousandFifteenMember		          
Long-term Line of Credit   152,500,000us-gaap_LineOfCredit
/ us-gaap_LongtermDebtTypeAxis
= udr_UnsecuredRevolvingCreditFacilityDueOctoberTwoThousandFifteenMember		   152,500,000us-gaap_LineOfCredit
/ us-gaap_LongtermDebtTypeAxis
= udr_UnsecuredRevolvingCreditFacilityDueOctoberTwoThousandFifteenMember		 0us-gaap_LineOfCredit
/ us-gaap_LongtermDebtTypeAxis
= udr_UnsecuredRevolvingCreditFacilityDueOctoberTwoThousandFifteenMember		    
4.63% Medium-Term Notes due January 2022              
Secured Debt (Textual) [Abstract]              
Unamortized fair market adjustment   2,523,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		   2,523,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		 2,882,000us-gaap_DebtInstrumentUnamortizedDiscount
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		    
Weighted Average Interest Rate   4.63%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		          
Fixed interest rate   4.63%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		   4.63%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		 4.63%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		    
Senior Notes   397,477,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		   397,477,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		 397,118,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FourPointSixThreePercentTermMediumNotesDueJanuaryTwoThousandTwentyTwoMember		    
2.68% Term Notes due December 2016              
Secured Debt (Textual) [Abstract]              
Weighted Average Interest Rate   1.53%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= udr_Twopointsixeightpercenttermnotesduedecember2016Member		          
Fixed interest rate   1.53%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_Twopointsixeightpercenttermnotesduedecember2016Member		   1.53%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_Twopointsixeightpercenttermnotesduedecember2016Member		 2.68%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_Twopointsixeightpercenttermnotesduedecember2016Member		    
Senior Notes   100,000,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_Twopointsixeightpercenttermnotesduedecember2016Member		   100,000,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_Twopointsixeightpercenttermnotesduedecember2016Member		 65,000,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_Twopointsixeightpercenttermnotesduedecember2016Member		    
ThreePointSevenTermNotesDueOctober2020 [Member]              
Secured Debt (Textual) [Abstract]              
Debt Instrument, Maturity Date           Oct. 31, 2020  
Debt Instrument, Face Amount         300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= udr_ThreePointSevenTermNotesDueOctober2020Member		    
Senior Notes   299,954,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_ThreePointSevenTermNotesDueOctober2020Member		   299,954,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_ThreePointSevenTermNotesDueOctober2020Member		 299,946,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_ThreePointSevenTermNotesDueOctober2020Member		    
Five Point One Three Percent, Medium Term Notes, Due January 2014 [Member]              
Secured Debt (Textual) [Abstract]              
Weighted Average Interest Rate   0.00%us-gaap_DebtInstrumentInterestRateDuringPeriod
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointOneThreePercentMediumTermNotesDueJanuary2014Member		          
Fixed interest rate   5.13%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointOneThreePercentMediumTermNotesDueJanuary2014Member		   5.13%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointOneThreePercentMediumTermNotesDueJanuary2014Member		 5.13%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointOneThreePercentMediumTermNotesDueJanuary2014Member		    
Senior Notes   0us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointOneThreePercentMediumTermNotesDueJanuary2014Member		   0us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointOneThreePercentMediumTermNotesDueJanuary2014Member		 184,000,000us-gaap_SeniorNotes
/ us-gaap_LongtermDebtTypeAxis
= udr_FivePointOneThreePercentMediumTermNotesDueJanuary2014Member		    
UDR Bank Credit Facility              
Secured Debt (Textual) [Abstract]              
Credit facilities with aggregate commitment   900,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		   900,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		 900,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		    
Increase in maximum borrowing capacity of unsecured revolving credit facility   1,450,000,000udr_IncrementInUnsecuredRevolvingCreditFacilityUnderCertainCircumstances
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		   1,450,000,000udr_IncrementInUnsecuredRevolvingCreditFacilityUnderCertainCircumstances
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		      
Long-term Line of Credit   152,500,000us-gaap_LineOfCredit
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		   152,500,000us-gaap_LineOfCredit
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		 0us-gaap_LineOfCredit
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		    
Interest rate at the end of the period   1.10%us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		   1.10%us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		 1.30%us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
/ us-gaap_LineOfCreditFacilityAxis
= udr_UdrBankCreditFacilityMember		    
Beginning of range of initial term of debt [Member] | Fannie Mae credit facilities              
Secured Debt (Textual) [Abstract]              
Debt Instrument, Term       7 years      
End of range of inital term of debt [Member] | Fannie Mae credit facilities              
Secured Debt (Textual) [Abstract]              
Debt Instrument, Term       10 years      
Fair Value, Measurements, Recurring [Member] | Line of Credit [Member] | Reported Value Measurement [Member] | Fannie Mae credit facilities | Fixed Rate Debt              
Secured Debt (Textual) [Abstract]              
Secured Debt Including Debt on Real Estate Held for Sale   568,086,000udr_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		   568,086,000udr_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		      
Fair Value, Measurements, Recurring [Member] | Line of Credit [Member] | Reported Value Measurement [Member] | Fannie Mae credit facilities | Variable Rate Debt              
Secured Debt (Textual) [Abstract]              
Secured Debt Including Debt on Real Estate Held for Sale   266,196,000udr_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		   266,196,000udr_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		      
Fair Value, Measurements, Recurring [Member] | Mortgages [Member] | Reported Value Measurement [Member] | Mortgages [Member] | Fixed Rate Debt              
Secured Debt (Textual) [Abstract]              
Secured Debt Including Debt on Real Estate Held for Sale   401,210,000udr_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		   401,210,000udr_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		      
Fair Value, Measurements, Recurring [Member] | Mortgages [Member] | Reported Value Measurement [Member] | Mortgages [Member] | Variable Rate Debt              
Secured Debt (Textual) [Abstract]              
Secured Debt Including Debt on Real Estate Held for Sale   $ 31,337,000udr_SecuredDebtIncludingDebtOnRealEstateHeldForSale
/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_FairValueByAssetClassAxis
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/ us-gaap_FairValueByMeasurementBasisAxis
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/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_LongtermDebtTypeAxis
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/ us-gaap_DebtInstrumentAxis
= udr_VariableRateDebtMember
/ us-gaap_FairValueByAssetClassAxis
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/ us-gaap_FairValueByMeasurementBasisAxis
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