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Significant Accounting Policies (Details) (USD $)
 1 Months Ended 3 Months Ended 12 Months Ended
Jul. 31, 2014
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
May 31, 2012
Accounting Policies [Line Items]                          
Document Period End Date                   Dec. 31, 2014      
Significant Accounting Policies (Textual) [Abstract]                          
Development costs excluding direct costs and capitalized interest                   $ 8,953,000udr_DevelopmentCostsExcludingDirectCostsAndCapitlizedInterest $ 11,100,000udr_DevelopmentCostsExcludingDirectCostsAndCapitlizedInterest $ 10,000,000udr_DevelopmentCostsExcludingDirectCostsAndCapitlizedInterest  
Interest capitalized during period                   20,200,000us-gaap_InterestCostsIncurredCapitalized 29,400,000us-gaap_InterestCostsIncurredCapitalized 26,400,000us-gaap_InterestCostsIncurredCapitalized  
Notes receivable   14,369,000us-gaap_NotesReceivableNet       83,033,000us-gaap_NotesReceivableNet       14,369,000us-gaap_NotesReceivableNet 83,033,000us-gaap_NotesReceivableNet    
Note maturity public capital threshold                   5,000,000udr_AmountOfPrivateOrPublicCapitalThatMustBeRaisedForNoteReceivableToMature      
Note receivable interest income           3,400,000us-gaap_OtherInterestAndDividendIncome         4,100,000us-gaap_OtherInterestAndDividendIncome 2,700,000us-gaap_OtherInterestAndDividendIncome  
Deferred tax asset   6,976,000us-gaap_DeferredTaxAssetsLiabilitiesNet       32,273,000us-gaap_DeferredTaxAssetsLiabilitiesNet       6,976,000us-gaap_DeferredTaxAssetsLiabilitiesNet 32,273,000us-gaap_DeferredTaxAssetsLiabilitiesNet 24,175,000us-gaap_DeferredTaxAssetsLiabilitiesNet  
Net of a valuation allowance   0us-gaap_DeferredTaxAssetsValuationAllowance       1,310,000us-gaap_DeferredTaxAssetsValuationAllowance       0us-gaap_DeferredTaxAssetsValuationAllowance 1,310,000us-gaap_DeferredTaxAssetsValuationAllowance 1,390,000us-gaap_DeferredTaxAssetsValuationAllowance  
Valuation Allowance, Deferred Tax Asset, Change in Amount                   400,000us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount   44,400,000us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount  
Income tax benefit resulting in change in valuation allowance                        (21,500,000)udr_IncomeTaxExpenseBenefitContinuingOperationsChangeInValuationAllowance  
Numerator for earnings per share — basic and diluted:                          
Net (loss)/income attributable to common stockholders   64,486,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 39,618,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 29,076,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 17,430,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 35,769,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 2,257,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 4,261,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic (1,199,000)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 150,610,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 41,088,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 203,376,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic  
Weighted average common shares outstanding                   252,707,000us-gaap_WeightedAverageNumberOfSharesIssuedBasic 250,684,000us-gaap_WeightedAverageNumberOfSharesIssuedBasic 239,482,000us-gaap_WeightedAverageNumberOfSharesIssuedBasic  
Weighted Average Number of Shares Outstanding, Basic and Diluted                   251,528,000us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted 249,969,000us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted 238,851,000us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted  
Net income/(loss) attributable to common stockholders — basic and diluted (in dollars per share)   $ 0.25us-gaap_EarningsPerShareBasicAndDiluted [1] $ 0.16us-gaap_EarningsPerShareBasicAndDiluted [1] $ 0.12us-gaap_EarningsPerShareBasicAndDiluted [1] $ 0.07us-gaap_EarningsPerShareBasicAndDiluted [1] $ 0.14us-gaap_EarningsPerShareBasicAndDiluted [1] $ 0.01us-gaap_EarningsPerShareBasicAndDiluted [1] $ 0.02us-gaap_EarningsPerShareBasicAndDiluted [1] $ 0.00us-gaap_EarningsPerShareBasicAndDiluted [1]        
Advertising expense                   6,000,000us-gaap_AdvertisingExpense 5,700,000us-gaap_AdvertisingExpense 6,200,000us-gaap_AdvertisingExpense  
(Decrease)/increase in net income (loss)                   0us-gaap_PreferredStockRedemptionPremium 0us-gaap_PreferredStockRedemptionPremium (2,791,000)us-gaap_PreferredStockRedemptionPremium  
Income Tax Expense (benefits), Discontinued Operations, Change in Valuation Allowance                       22,900,000udr_IncomeTaxExpensebenefitsDiscontinuedOperationsChangeinValuationAllowance  
Income Tax Expense (Benefit)                   25,994,000us-gaap_IncomeTaxExpenseBenefit (8,281,000)us-gaap_IncomeTaxExpenseBenefit (21,076,000)us-gaap_IncomeTaxExpenseBenefit  
Income Tax Examination, Likelihood of Unfavorable Settlement   not (greater than 50 percent probability)                      
Income Tax Examination, Penalties and Interest Accrued   0us-gaap_IncomeTaxExaminationPenaltiesAndInterestAccrued               0us-gaap_IncomeTaxExaminationPenaltiesAndInterestAccrued      
Minimum Percentage of Carrying Value Of Real Estate Portfolio Held By Company                       0.10udr_MinimumPercentageOfCarryingValueOfRealEstatePortfolioHeldByCompany  
Interest Income, Related Party                   0us-gaap_InterestIncomeRelatedParty 765,000us-gaap_InterestIncomeRelatedParty 281,000us-gaap_InterestIncomeRelatedParty  
(Issuance)/repayment of notes receivable                   68,664,000us-gaap_ProceedsFromSaleAndCollectionOfNotesReceivable (19,027,000)us-gaap_ProceedsFromSaleAndCollectionOfNotesReceivable (63,998,000)us-gaap_ProceedsFromSaleAndCollectionOfNotesReceivable  
Gain (Loss) on Sale of Notes Receivable 8,400,000us-gaap_GainLossOnSaleOfNotesReceivable                        
6.75% Series G Cumulative Redeemable Preferred Stock                          
Numerator for earnings per share — basic and diluted:                          
Preferred stock, dividend rate                       6.75%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesGPreferredStockMember		  
Preferred stock, shares redeemed                       3,264,362us-gaap_StockRedeemedOrCalledDuringPeriodShares
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesGPreferredStockMember		  
Preferred stock, redemption price per share                         $ 25us-gaap_PreferredStockRedemptionPricePerShare
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesGPreferredStockMember
Preferred stock, redemption amount                         82,100,000us-gaap_PreferredStockRedemptionAmount
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesGPreferredStockMember
Note Due March 2014 Related Party [Domain]                          
Significant Accounting Policies (Textual) [Abstract]                          
Basis spread on variable rate   35000.00%us-gaap_LoansReceivableBasisSpreadOnVariableRate
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_NoteDueMarch2014RelatedPartyDomain		               35000.00%us-gaap_LoansReceivableBasisSpreadOnVariableRate
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_NoteDueMarch2014RelatedPartyDomain		      
Note due October 2014 - related party                          
Significant Accounting Policies (Textual) [Abstract]                          
Notes receivable   0us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Notedueoctober2014RelatedpartyMember		       40,800,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Notedueoctober2014RelatedpartyMember		       0us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Notedueoctober2014RelatedpartyMember		 40,800,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Notedueoctober2014RelatedpartyMember		    
Note due February 2017                          
Significant Accounting Policies (Textual) [Abstract]                          
Notes receivable   11,869,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		       14,580,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		       11,869,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		 14,580,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		    
Note Receivable Interest Rate   10.00%udr_NoteReceivableInterestRate
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		               10.00%udr_NoteReceivableInterestRate
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		      
Increase (Decrease) in Notes Receivables                   1,200,000us-gaap_IncreaseDecreaseInNotesReceivables
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		      
Note maturity public capital threshold                   5,000,000udr_AmountOfPrivateOrPublicCapitalThatMustBeRaisedForNoteReceivableToMature
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		      
Proceeds from Collection of Notes Receivable                   3,900,000us-gaap_ProceedsFromCollectionOfNotesReceivable
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduefebruary2017Member		      
Note due June 2022 (net of discount of $283)                          
Significant Accounting Policies (Textual) [Abstract]                          
Notes receivable   0us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		       26,253,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		       0us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		 26,253,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		 26,500,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		  
Note Receivable Interest Rate                       7.00%udr_NoteReceivableInterestRate
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		  
Note receivable, unamortized discount   0us-gaap_ReceivableWithImputedInterestDiscount
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		       0us-gaap_ReceivableWithImputedInterestDiscount
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		       0us-gaap_ReceivableWithImputedInterestDiscount
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		 0us-gaap_ReceivableWithImputedInterestDiscount
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		    
Discount rate on note receivable                       7.25%udr_Discountrateonnotereceivable
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		  
Numerator for earnings per share — basic and diluted:                          
(Issuance)/repayment of notes receivable 36,000,000us-gaap_ProceedsFromSaleAndCollectionOfNotesReceivable
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejune2022Member		                        
Other                          
Significant Accounting Policies (Textual) [Abstract]                          
Notes receivable   2,500,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejuly2017Member		       1,400,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejuly2017Member		       2,500,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejuly2017Member		 1,400,000us-gaap_NotesReceivableNet
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejuly2017Member		    
Note Receivable Interest Rate   8.00%udr_NoteReceivableInterestRate
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejuly2017Member		               8.00%udr_NoteReceivableInterestRate
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejuly2017Member		      
Increase (Decrease) in Notes Receivables                   1,100,000us-gaap_IncreaseDecreaseInNotesReceivables
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= udr_Noteduejuly2017Member		      
OP Units                          
Numerator for earnings per share — basic and diluted:                          
Antidilutive securities                   9,247,049us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EquityUnitPurchaseAgreementsMember		 9,337,464us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EquityUnitPurchaseAgreementsMember		 9,411,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EquityUnitPurchaseAgreementsMember		  
Preferred Stock                          
Numerator for earnings per share — basic and diluted:                          
Antidilutive securities                   3,035,548us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_ConvertiblePreferredStockMember		 3,035,548us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_ConvertiblePreferredStockMember		 3,036,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_ConvertiblePreferredStockMember		  
Stock options and unvested restricted stock                          
Numerator for earnings per share — basic and diluted:                          
Antidilutive securities                   1,916,979us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_StockCompensationPlanMember		 1,583,537us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_StockCompensationPlanMember		 1,361,398us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_StockCompensationPlanMember		  
Minimum | Buildings                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   35 years      
Minimum | Building improvements                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   10 years      
Minimum | Furniture, fixtures, equipment, and other assets                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   3 years      
Maximum | Buildings                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   55 years      
Maximum | Building improvements                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   35 years      
Maximum | Furniture, fixtures, equipment, and other assets                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   10 years      
RedeemableNoncontrollingInterest [Member]                          
Accounting Policies [Line Items]                          
Other Comprehensive (Income) Loss, Net of Tax, Portion Attributable to Noncontrolling Interest                   (133,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest
/ udr_NoncontrollinginteresttypeAxis
= udr_RedeemablenoncontrollinginterestMember		 250,000us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest
/ udr_NoncontrollinginteresttypeAxis
= udr_RedeemablenoncontrollinginterestMember		 80,000us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest
/ udr_NoncontrollinginteresttypeAxis
= udr_RedeemablenoncontrollinginterestMember		  
Continuing Operations [Member]                          
Numerator for earnings per share — basic and diluted:                          
Income Tax Expense (Benefit)                   (15,098,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementOperatingActivitiesSegmentAxis
= us-gaap_SegmentContinuingOperationsMember		 (7,299,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementOperatingActivitiesSegmentAxis
= us-gaap_SegmentContinuingOperationsMember		 (30,282,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementOperatingActivitiesSegmentAxis
= us-gaap_SegmentContinuingOperationsMember		  
Discontinued Operations [Member]                          
Numerator for earnings per share — basic and diluted:                          
Income Tax Expense (Benefit)                   5,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementOperatingActivitiesSegmentAxis
= us-gaap_SegmentDiscontinuedOperationsMember		 (982,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementOperatingActivitiesSegmentAxis
= us-gaap_SegmentDiscontinuedOperationsMember		 9,641,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementOperatingActivitiesSegmentAxis
= us-gaap_SegmentDiscontinuedOperationsMember		  
Lodge at Stoughton                          
Significant Accounting Policies (Textual) [Abstract]                          
Equity Method Investment, Ownership Percentage           95.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= udr_UnconsolidatedJointVentureTwoStoughtonMassachusettsMember		         95.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= udr_UnconsolidatedJointVentureTwoStoughtonMassachusettsMember		    
Joint Venture Number of Operating Communities Owned   1udr_JointVentureNumberOfOperatingCommunitiesOwned
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= udr_UnconsolidatedJointVentureTwoStoughtonMassachusettsMember		               1udr_JointVentureNumberOfOperatingCommunitiesOwned
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= udr_UnconsolidatedJointVentureTwoStoughtonMassachusettsMember		      
Number of extension options on loan                   2udr_Numberofextensionoptionsonloan
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= udr_UnconsolidatedJointVentureTwoStoughtonMassachusettsMember		      
Extension period of option on loan                   3 months      
United Dominion Reality L P [Member]                          
Accounting Policies [Line Items]                          
Document Period End Date                   Dec. 31, 2014      
Deferred Tax Liabilities, Net   0us-gaap_DeferredTaxLiabilities
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		               0us-gaap_DeferredTaxLiabilities
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		      
Significant Accounting Policies (Textual) [Abstract]                          
Development costs excluding direct costs and capitalized interest                   2,010,000udr_DevelopmentCostsExcludingDirectCostsAndCapitlizedInterest
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		 2,500,000udr_DevelopmentCostsExcludingDirectCostsAndCapitlizedInterest
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		 2,100,000udr_DevelopmentCostsExcludingDirectCostsAndCapitlizedInterest
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		  
Interest capitalized during period                   2,900,000us-gaap_InterestCostsIncurredCapitalized
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		 5,900,000us-gaap_InterestCostsIncurredCapitalized
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		 3,700,000us-gaap_InterestCostsIncurredCapitalized
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		  
Numerator for earnings per share — basic and diluted:                          
Advertising expense                   2,500,000us-gaap_AdvertisingExpense
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		 2,500,000us-gaap_AdvertisingExpense
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		 2,400,000us-gaap_AdvertisingExpense
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		  
Minimum Percentage of Carrying Value Of Real Estate Portfolio Held By Company                   0.10udr_MinimumPercentageOfCarryingValueOfRealEstatePortfolioHeldByCompany
/ dei_LegalEntityAxis
= udr_UnitedDominionRealityLPMember		      
United Dominion Reality L P [Member] | Minimum | Buildings                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   35 years      
United Dominion Reality L P [Member] | Minimum | Building improvements                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   10 years      
United Dominion Reality L P [Member] | Minimum | Furniture, fixtures, equipment, and other assets                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   3 years      
United Dominion Reality L P [Member] | Maximum | Buildings                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   55 years      
United Dominion Reality L P [Member] | Maximum | Building improvements                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   35 years      
United Dominion Reality L P [Member] | Maximum | Furniture, fixtures, equipment, and other assets                          
Significant Accounting Policies (Textual) [Abstract]                          
Estimated useful lives                   10 years      
Preferred Stock                          
Numerator for earnings per share — basic and diluted:                          
Preferred stock, shares redeemed                   0us-gaap_StockRedeemedOrCalledDuringPeriodShares
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_PreferredStockMember		    3,264,362us-gaap_StockRedeemedOrCalledDuringPeriodShares
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_PreferredStockMember		  
Reported Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]                          
Significant Accounting Policies (Textual) [Abstract]                          
Notes receivable   $ 14,369,000us-gaap_NotesReceivableNet
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		       $ 83,033,000us-gaap_NotesReceivableNet
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		       $ 14,369,000us-gaap_NotesReceivableNet
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 $ 83,033,000us-gaap_NotesReceivableNet
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		    
[1] Quarterly income/(loss) per share amounts may not total to the annual amounts.