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Employee Benefit Plans (Details Textual) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Issued 4,517,514udr_SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsIssued      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number 2,265,842us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 2,430,127us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value $ 4,800,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1      
Number of share options exercisable 2,265,842us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber 2,430,127us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber    
Range One        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of share options exercisable 1,830,672us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= udr_RangeOneMember
     
Share options exercise price, lower range limit $ 10.06us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= udr_RangeOneMember
     
Range Two        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of share options exercisable 404,291us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= udr_RangeTwoMember
     
Share options exercise price, lower range limit $ 24.38us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= udr_RangeTwoMember
     
Range Three        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of share options exercisable 30,879us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= udr_RangeThreeMember
     
Share options exercise price, upper range limit $ 25.10us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= udr_RangeThreeMember
     
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total remaining compensation cost related to unvested share options 0us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
     
Stock based compensation expense 0us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
0us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
100,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
 
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total remaining compensation cost related to unvested share options 2,500,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
     
Weighted average remaining contractual life 1 year 1 month      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value $ 23.14us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
     
Stock based compensation expense 4,200,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
3,600,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
3,700,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
 
Restricted Stock | Minimum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 3 years      
Restricted Stock | Maximum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 4 years      
Long Term Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total remaining compensation cost related to unvested share options 5,800,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= udr_LongTermIncentivePlanMember
     
Weighted average remaining contractual life 1 year 10 months      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value $ 21.15us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= udr_LongTermIncentivePlanMember
$ 21.97us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= udr_LongTermIncentivePlanMember
   
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate 23.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= udr_LongTermIncentivePlanMember
15.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= udr_LongTermIncentivePlanMember
   
Stock based compensation expense 9,800,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= udr_LongTermIncentivePlanMember
5,900,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= udr_LongTermIncentivePlanMember
4,900,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= udr_LongTermIncentivePlanMember
 
Long Term Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares reserved for issuance under plan 19,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= udr_LongTermIncentivePlanMember
    16,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= udr_LongTermIncentivePlanMember
Shares available for issuance under plan 10,067,371us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= udr_LongTermIncentivePlanMember
     
Profit Sharing Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Aggregate provisions for contributions $ 900,000us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
/ us-gaap_PlanNameAxis
= udr_ProfitSharingPlanMember
$ 900,000us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
/ us-gaap_PlanNameAxis
= udr_ProfitSharingPlanMember
$ 600,000us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
/ us-gaap_PlanNameAxis
= udr_ProfitSharingPlanMember