Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Narrative (Details)

v2.4.1.9
Stock Based Compensation - Narrative (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Apr. 23, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of Potential Award Based Upon Service Requirement 15.00%wre_PercentageofPotentialAwardBasedUponServiceRequirement      
Percentage of potential award based upon strategic plan fulfillment 20.00%wre_PercentageOfPotentialAwardBasedUponStrategicPlanFulfillment      
Award vesting period 1 year      
Trustee share-based compensation $ 55,000wre_TrusteeShareBasedCompensation $ 55,000wre_TrusteeShareBasedCompensation $ 55,000wre_TrusteeShareBasedCompensation  
Allocated Share-based Compensation Expense 4,995,000us-gaap_AllocatedShareBasedCompensationExpense 6,246,000us-gaap_AllocatedShareBasedCompensationExpense 5,856,000us-gaap_AllocatedShareBasedCompensationExpense  
Fair value of restricted share units vested 6,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue 3,800,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue 5,600,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue  
Restricted Share Awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total compensation cost not yet recognized, period for recognition 17 months      
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized 1,200,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= wre_RestrictedShareAwardsMember
     
Washington Real Estate Investment Trust 2007 Omnibus Long Term Incentive Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized 2,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= wre_WashingtonRealEstateInvestmentTrust2007OmnibusLongTermIncentivePlanMember
     
Plan in effect, period 10 years      
Options outstanding 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= wre_WashingtonRealEstateInvestmentTrust2007OmnibusLongTermIncentivePlanMember
     
New STIP [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of Potential Award Based Upon Service Requirement 50.00%wre_PercentageofPotentialAwardBasedUponServiceRequirement
/ us-gaap_PlanNameAxis
= wre_NewStipMember
     
Awards, Vested after Performance Period, Percentage 50.00%wre_SharebasedCompensationArrangementsbySharebasedPaymentAwardsOptionsVestedafterPerformancePeriodPercentage
/ us-gaap_PlanNameAxis
= wre_NewStipMember
     
Performance period 1 year      
New STIP [Member] | Performance-Based Awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award vesting period 3 years      
New LTIP [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage payable In unrestricted shares 75.00%wre_PercentagePayableInUnrestrictedShares
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Percentage payable in restricted shares 25.00%wre_PercentagePayableInRestrictedShares
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Award vesting period 3 years      
Awards, Vested after Performance Period, Percentage 75.00%wre_SharebasedCompensationArrangementsbySharebasedPaymentAwardsOptionsVestedafterPerformancePeriodPercentage
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Awards, Vested after Performance Period, Additional Service Period, Percentage 25.00%wre_SharebasedCompensationArrangementsbySharebasedPaymentAwardsOptionsVestedafterPerformancePeriodAdditionalServicePeriodPercentage
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Performance period 3 years      
Total compensation cost not yet recognized, period for recognition 4 years      
Percentage of Potential Award Based Upon absolute TSR 50.00%wre_PercentageofPotentialAwardBasedUponabsoluteTSR
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Percentage of Potential Award Based Upon relative TSR 50.00%wre_PercentageofPotentialAwardBasedUponrelativeTSR
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Grant date fair value as a percentage of base salary 150.00%wre_GrantDateFairValueAsPercentageOfBaseSalary
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Weighting for performance measurement based on cumulative 3-Year total shareholder return 50.00%wre_WeightingForPerformanceMeasurementBasedOnCumulative3YearTotalShareholderReturn
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Weighting for performance measurement based on 20 peer comapnies 50.00%wre_WeightingForPerformanceMeasurementBasedOn20PeerComapnies
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Fair value assumptions, expected volatility rate 23.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Fair value assumptions, risk free interest rate 0.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
     
Closing share price, date of grant       $ 24.08wre_ClosingSharePriceDateOfGrant
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
New LTIP [Member] | Minimum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance period 1 year      
Grant date fair value as a percentage of base salary 80.00%wre_GrantDateFairValueAsPercentageOfBaseSalary
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
     
Fair value assumptions, expected term 3 years      
Grant Date Fair Value as a Percentage of Base Salary on absolute TSR 20.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonabsoluteTSR
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
     
Grant Date Fair Value as a Percentage of Base Salary on relative TSR 35.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonrelativeTSR
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
     
Grant Date Fair Value as a Percentage of Base Salary on absolute TSR transition year one 10.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonabsoluteTSRtransitionyearone
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
     
Grant Date Fair Value as a Percentage of Base Salary on relative TSR transition year one 11.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonrelativeTSRtransitionyearone
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
     
Grant Date Fair Value as a Percentage of Base Salary on relative TSR transition year two 23.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonrelativeTSRtransitionyeartwo
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
     
Grant Date Fair Value as a Percentage of Base Salary on absolute TSR transition year two 16.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonabsoluteTSRtransitionyeartwo
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
     
New LTIP [Member] | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance period 2 years      
Fair value assumptions, expected term 4 years      
Grant Date Fair Value as a Percentage of Base Salary on absolute TSR 38.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonabsoluteTSR
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
     
Grant Date Fair Value as a Percentage of Base Salary on relative TSR 67.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonrelativeTSR
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
     
Grant Date Fair Value as a Percentage of Base Salary on absolute TSR transition year one 20.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonabsoluteTSRtransitionyearone
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
     
Grant Date Fair Value as a Percentage of Base Salary on relative TSR transition year one 20.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonrelativeTSRtransitionyearone
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
     
Grant Date Fair Value as a Percentage of Base Salary on relative TSR transition year two 43.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonrelativeTSRtransitionyeartwo
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
     
Grant Date Fair Value as a Percentage of Base Salary on absolute TSR transition year two 30.00%wre_GrantDateFairValueasaPercentageofBaseSalaryonabsoluteTSRtransitionyeartwo
/ us-gaap_PlanNameAxis
= wre_NewLtipMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
     
Cash [Member] | New STIP [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage payable In unrestricted shares 100.00%wre_PercentagePayableInUnrestrictedShares
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_CashMember
/ us-gaap_PlanNameAxis
= wre_NewStipMember
     
Cash [Member] | New STIP [Member] | Performance-Based Awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage payable In unrestricted shares 50.00%wre_PercentagePayableInUnrestrictedShares
/ us-gaap_AwardTypeAxis
= wre_PerformanceBasedAwardsMember
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_CashMember
/ us-gaap_PlanNameAxis
= wre_NewStipMember
     
Unrestricted Share Awards [Member] | New LTIP [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total compensation cost not yet recognized, period for recognition 3 years      
Restricted Share Units [Member] | New STIP [Member] | Performance-Based Awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage payable in restricted shares 50.00%wre_PercentagePayableInRestrictedShares
/ us-gaap_AwardTypeAxis
= wre_PerformanceBasedAwardsMember
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= wre_RestrictedShareUnitsMember
/ us-gaap_PlanNameAxis
= wre_NewStipMember
     
Restricted Share Units [Member] | New LTIP [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance period 1 year      
Restricted Share Units [Member] | New LTIP [Member] | Performance-Based Awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total compensation cost not yet recognized, period for recognition 4 years      
Chief Executive Officer [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost $ 1,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ChiefExecutiveOfficerMember