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Real Estate Real Estate (Details) (USD $)
12 Months Ended 60 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Land $ 6,295,404,000us-gaap_Land $ 6,192,512,000us-gaap_Land   $ 6,295,404,000us-gaap_Land
Depreciable property Abstract        
Investment Building and Building Improvements 17,974,337,000us-gaap_InvestmentBuildingAndBuildingImprovements 17,509,609,000us-gaap_InvestmentBuildingAndBuildingImprovements   17,974,337,000us-gaap_InvestmentBuildingAndBuildingImprovements
Fixtures and Equipment, Gross 1,365,276,000us-gaap_FixturesAndEquipmentGross 1,214,220,000us-gaap_FixturesAndEquipmentGross   1,365,276,000us-gaap_FixturesAndEquipmentGross
Finite-Lived Intangible Assets, Gross 511,891,000us-gaap_FiniteLivedIntangibleAssetsGross 502,218,000us-gaap_FiniteLivedIntangibleAssetsGross   511,891,000us-gaap_FiniteLivedIntangibleAssetsGross
Development in Process 1,343,919,000us-gaap_DevelopmentInProcess 988,867,000us-gaap_DevelopmentInProcess   1,343,919,000us-gaap_DevelopmentInProcess
Land Available for Development 184,556,000us-gaap_LandAvailableForDevelopment 393,522,000us-gaap_LandAvailableForDevelopment   184,556,000us-gaap_LandAvailableForDevelopment
Investment in real estate 27,675,383,000us-gaap_RealEstateInvestmentPropertyAtCost 26,800,948,000us-gaap_RealEstateInvestmentPropertyAtCost   27,675,383,000us-gaap_RealEstateInvestmentPropertyAtCost
Accumulated depreciation 5,432,805,000us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation 4,807,709,000us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation   5,432,805,000us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation
Investment in real estate, net 22,242,578,000us-gaap_RealEstateInvestmentPropertyNet 21,993,239,000us-gaap_RealEstateInvestmentPropertyNet   22,242,578,000us-gaap_RealEstateInvestmentPropertyNet
Ground Lease Intangibles Below Market 178,251,000eqr_GroundLeaseIntangiblesBelowMarket 178,251,000eqr_GroundLeaseIntangiblesBelowMarket   178,251,000eqr_GroundLeaseIntangiblesBelowMarket
Retail Lease Intangibles Above Market 1,260,000eqr_RetailLeaseIntangiblesAboveMarket 1,260,000eqr_RetailLeaseIntangiblesAboveMarket   1,260,000eqr_RetailLeaseIntangiblesAboveMarket
Lease Intangible Assets 179,511,000eqr_LeaseIntangibleAssets 179,511,000eqr_LeaseIntangibleAssets   179,511,000eqr_LeaseIntangibleAssets
Accumulated Amortization Intangible Assets (8,913,000)eqr_AccumulatedAmortizationIntangibleAssets (4,364,000)eqr_AccumulatedAmortizationIntangibleAssets   (8,913,000)eqr_AccumulatedAmortizationIntangibleAssets
Lease Intangible Assets, Net 170,598,000eqr_LeaseIntangibleAssetsNet 175,147,000eqr_LeaseIntangibleAssetsNet   170,598,000eqr_LeaseIntangibleAssetsNet
Ground Lease Intangibles Above Market 2,400,000eqr_GroundLeaseIntangiblesAboveMarket 2,400,000eqr_GroundLeaseIntangiblesAboveMarket   2,400,000eqr_GroundLeaseIntangiblesAboveMarket
Retail Lease Intangibles Below Market 5,270,000eqr_RetailLeaseIntangiblesBelowMarket 5,500,000eqr_RetailLeaseIntangiblesBelowMarket   5,270,000eqr_RetailLeaseIntangiblesBelowMarket
Lease Intangible Liabilities 7,670,000eqr_LeaseIntangibleLiabilities 7,900,000eqr_LeaseIntangibleLiabilities   7,670,000eqr_LeaseIntangibleLiabilities
Amortization Of Intangible Liabilities (2,258,000)eqr_AmortizationOfIntangibleLiabilities (1,161,000)eqr_AmortizationOfIntangibleLiabilities   (2,258,000)eqr_AmortizationOfIntangibleLiabilities
Lease Intangible Liabilities, net 5,412,000eqr_LeaseIntangibleLiabilitiesNet 6,739,000eqr_LeaseIntangibleLiabilitiesNet   5,412,000eqr_LeaseIntangibleLiabilitiesNet
Ground Lease Amortization 4,300,000eqr_GroundLeaseAmortization 3,600,000eqr_GroundLeaseAmortization    
Cost of Property Repairs and Maintenance 473,098,000us-gaap_CostOfPropertyRepairsAndMaintenance 449,427,000us-gaap_CostOfPropertyRepairsAndMaintenance 332,219,000us-gaap_CostOfPropertyRepairsAndMaintenance  
Weighted Average Ground Lease Amortization Period 49.8eqr_WeightedAverageGroundLeaseAmortizationPeriod     49.8eqr_WeightedAverageGroundLeaseAmortizationPeriod
Weighted Average Retail Lease Amortization Period 2.8eqr_WeightedAverageRetailLeaseAmortizationPeriod     2.8eqr_WeightedAverageRetailLeaseAmortizationPeriod
Properties acquired     1eqr_PropertiesAcquired  
Master Leased Properties Acquired 3eqr_MasterLeasedPropertiesAcquired     3eqr_MasterLeasedPropertiesAcquired
Acquisition of Archstone, net of cash acquired 0us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired 4,000,875,000us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired 0us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired  
Mortgage notes payable 5,086,515,000us-gaap_SecuredDebt 5,174,166,000us-gaap_SecuredDebt   5,086,515,000us-gaap_SecuredDebt
Stock Issued During Period, Shares, New Issues 0us-gaap_StockIssuedDuringPeriodSharesNewIssues 34,468,085us-gaap_StockIssuedDuringPeriodSharesNewIssues 25,023,919us-gaap_StockIssuedDuringPeriodSharesNewIssues  
Acquisition of Archstone Common Shares Issued 0eqr_AcquisitionOfArchstoneCommonSharesIssued 1,929,868,000eqr_AcquisitionOfArchstoneCommonSharesIssued 0eqr_AcquisitionOfArchstoneCommonSharesIssued  
Average Price Per Common Share Issued     $ 60.59eqr_AveragePricePerCommonShareIssued  
Noncash or Part Noncash Acquisition, Debt Assumed 28,900,000us-gaap_NoncashOrPartNoncashAcquisitionDebtAssumed1 34,100,000us-gaap_NoncashOrPartNoncashAcquisitionDebtAssumed1    
Mark-to-Market Debt Premiums   127,900,000eqr_MarkToMarketDebtPremiums    
Stock Issued During Period Shares   21,850,000eqr_StockIssuedDuringPeriodShares    
Stock Issued During Period, Value, New Issues     192,300,000us-gaap_StockIssuedDuringPeriodValueNewIssues  
Proceeds from Sale of Other Assets   4,500,000,000us-gaap_ProceedsFromSaleOfOtherAssets1    
Number Of Operating Properties Under Long Term Ground Leases 13eqr_NumberOfOperatingPropertiesUnderLongTermGroundLeases     13eqr_NumberOfOperatingPropertiesUnderLongTermGroundLeases
Business Combination, Acquisition Related Costs 400,000us-gaap_BusinessCombinationAcquisitionRelatedCosts 300,000us-gaap_BusinessCombinationAcquisitionRelatedCosts 7,000,000us-gaap_BusinessCombinationAcquisitionRelatedCosts  
Payments of Financing Costs 10,982,000us-gaap_PaymentsOfFinancingCosts 16,526,000us-gaap_PaymentsOfFinancingCosts 21,209,000us-gaap_PaymentsOfFinancingCosts  
Merger Expenses   19,900,000eqr_MergerExpenses 5,600,000eqr_MergerExpenses 85,500,000eqr_MergerExpenses
(Loss) from investments in unconsolidated entities due to merger expenses (4,300,000)eqr_IncomeLossFromEquityMethodInvestmentsMergerExpenses (54,000,000)eqr_IncomeLossFromEquityMethodInvestmentsMergerExpenses    
Business Acquisition, Pro Forma Revenue   2,485,438,000us-gaap_BusinessAcquisitionsProFormaRevenue 2,317,699,000us-gaap_BusinessAcquisitionsProFormaRevenue  
Business Acquisition, Proforma Income Loss From Continuing Operations   203,286,000eqr_BusinessAcquisitionProformaIncomeLossFromContinuingOperations (54,940,000)eqr_BusinessAcquisitionProformaIncomeLossFromContinuingOperations  
Business Acquisition, Proforma Income Loss From Discontinued Operations Net Of Tax   2,074,072,000eqr_BusinessAcquisitionProformaIncomeLossFromDiscontinuedOperationsNetOfTax 720,361,000eqr_BusinessAcquisitionProformaIncomeLossFromDiscontinuedOperationsNetOfTax  
Business Acquisition, Pro Forma Net Income (Loss)   2,277,358,000us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss 665,421,000us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss  
Business Acquisition, Proforma Net Income Available to Common Shares   2,183,756,000eqr_BusinessAcquisitionProformaNetIncomeAvailableToCommonShares 622,424,000eqr_BusinessAcquisitionProformaNetIncomeAvailableToCommonShares  
Business Acquisition, Pro Forma Earnings Per Share, Basic   $ 6.07us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic $ 1.74us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic  
Business Acquisition, Proforma Weighted Average Common Shares Basic   359,688,000eqr_BusinessAcquisitionProformaWeightedAverageCommonSharesBasic 356,984,000eqr_BusinessAcquisitionProformaWeightedAverageCommonSharesBasic  
Business Acquisition, Pro Forma Earnings Per Share, Diluted   $ 6.05us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted $ 1.74us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted  
Business Acquisition, Proforma Weighted Average Number Of Shares Diluted   375,861,000eqr_BusinessAcquisitionProformaWeightedAverageNumberOfSharesDiluted 356,984,000eqr_BusinessAcquisitionProformaWeightedAverageNumberOfSharesDiluted  
Ground Lease [Member]        
Depreciable property Abstract        
Cost of Property Repairs and Maintenance 1,100,000us-gaap_CostOfPropertyRepairsAndMaintenance
/ us-gaap_StatementScenarioAxis
= eqr_GroundLeaseMember
2,700,000us-gaap_CostOfPropertyRepairsAndMaintenance
/ us-gaap_StatementScenarioAxis
= eqr_GroundLeaseMember
   
Unconsolidated Properties [Member]        
Depreciable property Abstract        
Uncompleted Development Properties Acquired   2eqr_UncompletedDevelopmentPropertiesAcquired
/ us-gaap_StatementScenarioAxis
= us-gaap_UnconsolidatedPropertiesMember
   
Consolidated Properties [Member]        
Depreciable property Abstract        
Uncompleted Development Properties Acquired   2eqr_UncompletedDevelopmentPropertiesAcquired
/ us-gaap_StatementScenarioAxis
= us-gaap_ConsolidatedPropertiesMember
   
Archstone [Member]        
Depreciable property Abstract        
Acquisition of Archstone, net of cash acquired   4,000,000,000us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Mortgage notes payable   2,000,000,000us-gaap_SecuredDebt
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Noncash or Part Noncash Acquisition, Debt Assumed   3,100,000,000us-gaap_NoncashOrPartNoncashAcquisitionDebtAssumed1
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Land   2,239,000,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLand
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles   304,830,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Business Combination Purchase Price Allocation Projects Under Development   36,583,000eqr_BusinessCombinationPurchasePriceAllocationProjectsUnderDevelopment
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Business Combination Purchase Price Allocation Land Held for Development   244,097,000eqr_BusinessCombinationPurchasePriceAllocationLandHeldForDevelopment
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Business Combination Purchase Price Allocation Investments in Unconsolidated Entities   230,608,000eqr_BusinessCombinationPurchasePriceAllocationInvestmentsInUnconsolidatedEntities
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets   195,260,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other   (108,997,000)us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
Payments of Financing Costs   2,500,000us-gaap_PaymentsOfFinancingCosts
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
8,400,000us-gaap_PaymentsOfFinancingCosts
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
13,500,000us-gaap_PaymentsOfFinancingCosts
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
Severance Costs   54,100,000us-gaap_SeveranceCosts1
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneMember
   
2015 [Member]        
Depreciable property Abstract        
Ground Lease Intangibles Amortization 5 Year 4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2015Member
    4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2015Member
Retail Lease Intangibles Amortization 5 Year (939,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2015Member
    (939,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2015Member
Total Above And Below Market Ground Lease Intangibles And Retail Lease Intangibles 5 Year 3,382,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2015Member
    3,382,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2015Member
2016 [Member]        
Depreciable property Abstract        
Ground Lease Intangibles Amortization 5 Year 4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2016Member
    4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2016Member
Retail Lease Intangibles Amortization 5 Year (896,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2016Member
    (896,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2016Member
Total Above And Below Market Ground Lease Intangibles And Retail Lease Intangibles 5 Year 3,425,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2016Member
    3,425,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2016Member
2017 [Member]        
Depreciable property Abstract        
Ground Lease Intangibles Amortization 5 Year 4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2017Member
    4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2017Member
Retail Lease Intangibles Amortization 5 Year (540,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2017Member
    (540,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2017Member
Total Above And Below Market Ground Lease Intangibles And Retail Lease Intangibles 5 Year 3,781,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2017Member
    3,781,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2017Member
2018 [Member]        
Depreciable property Abstract        
Ground Lease Intangibles Amortization 5 Year 4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2018Member
    4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2018Member
Retail Lease Intangibles Amortization 5 Year (71,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2018Member
    (71,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2018Member
Total Above And Below Market Ground Lease Intangibles And Retail Lease Intangibles 5 Year 4,250,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2018Member
    4,250,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2018Member
2019 [Member]        
Depreciable property Abstract        
Ground Lease Intangibles Amortization 5 Year 4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2019Member
    4,321,000eqr_GroundLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2019Member
Retail Lease Intangibles Amortization 5 Year (71,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2019Member
    (71,000)eqr_RetailLeaseIntangiblesAmortization5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2019Member
Total Above And Below Market Ground Lease Intangibles And Retail Lease Intangibles 5 Year 4,250,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2019Member
    4,250,000eqr_TotalAboveAndBelowMarketGroundLeaseIntangiblesAndRetailLeaseIntangibles5Year
/ us-gaap_StatementScenarioAxis
= eqr_A2019Member
Building and Building Improvements [Member]        
Depreciable property Abstract        
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment   5,765,538,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment
/ us-gaap_StatementScenarioAxis
= us-gaap_BuildingAndBuildingImprovementsMember
   
Furniture and Fixtures [Member]        
Depreciable property Abstract        
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment   61,470,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment
/ us-gaap_StatementScenarioAxis
= us-gaap_FurnitureAndFixturesMember
   
Archstone Transaction [Member]        
Depreciable property Abstract        
Ground Lease Intangibles Below Market   178,251,000eqr_GroundLeaseIntangiblesBelowMarket
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Retail Lease Intangibles Above Market   1,260,000eqr_RetailLeaseIntangiblesAboveMarket
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Ground Lease Intangibles Above Market   2,400,000eqr_GroundLeaseIntangiblesAboveMarket
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Retail Lease Intangibles Below Market   8,040,000eqr_RetailLeaseIntangiblesBelowMarket
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Business Acquisition, Percentage of Voting Interests Acquired 60.00%us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
    60.00%us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
Properties acquired   71eqr_PropertiesAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Partially Owned Consolidated Properties Acquired   1eqr_PartiallyOwnedConsolidatedPropertiesAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Partially Owned Consolidated Units Acquired   432eqr_PartiallyOwnedConsolidatedUnitsAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Partially Owned Unconsolidated Properties Acquired   1eqr_PartiallyOwnedUnconsolidatedPropertiesAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Partially Owned Unconsolidated Units Acquired   336eqr_PartiallyOwnedUnconsolidatedUnitsAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Master Leased Properties Acquired   3eqr_MasterLeasedPropertiesAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Master Leased Units Acquired   853eqr_MasterLeasedUnitsAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Uncompleted Development Properties Acquired   4eqr_UncompletedDevelopmentPropertiesAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Uncompleted Development Units Acquired   964eqr_UncompletedDevelopmentUnitsAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Land parcels acquired   14eqr_LandParcelsAcquired
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net   8,968,389,000us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual   514,700,000us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual   352,800,000us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Number Of Operating Properties Under Long Term Ground Leases   9eqr_NumberOfOperatingPropertiesUnderLongTermGroundLeases
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
   
Business Combination, Acquisition Related Costs 99,000,000us-gaap_BusinessCombinationAcquisitionRelatedCosts
/ us-gaap_StatementScenarioAxis
= eqr_ArchstoneTransactionMember
     
Projects under development [Member]        
Depreciable property Abstract        
Land Under Development 466,764,000eqr_LandUnderDevelopment
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_ProjectsUnderDevelopmentMember
353,574,000eqr_LandUnderDevelopment
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_ProjectsUnderDevelopmentMember
  466,764,000eqr_LandUnderDevelopment
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_ProjectsUnderDevelopmentMember
Development in Process 877,155,000us-gaap_DevelopmentInProcess
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_ProjectsUnderDevelopmentMember
635,293,000us-gaap_DevelopmentInProcess
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_ProjectsUnderDevelopmentMember
  877,155,000us-gaap_DevelopmentInProcess
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_ProjectsUnderDevelopmentMember
Land held for development [Member]        
Depreciable property Abstract        
Development in Process 39,190,000us-gaap_DevelopmentInProcess
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_LandHeldForDevelopmentMember
52,133,000us-gaap_DevelopmentInProcess
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_LandHeldForDevelopmentMember
  39,190,000us-gaap_DevelopmentInProcess
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_LandHeldForDevelopmentMember
Land Available for Development 145,366,000us-gaap_LandAvailableForDevelopment
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_LandHeldForDevelopmentMember
341,389,000us-gaap_LandAvailableForDevelopment
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_LandHeldForDevelopmentMember
  145,366,000us-gaap_LandAvailableForDevelopment
/ eqr_RealEstateAndAccumulatedDepreciationTypesOfPropertyAxis
= eqr_LandHeldForDevelopmentMember
Archstone Transaction [Member]        
Depreciable property Abstract        
Property Units Acquired   20,160eqr_PropertyUnitsAcquired
/ dei_LegalEntityAxis
= eqr_ArchstoneTransactionMember
   
OPERATING PARTNERSHIP        
Land 6,295,404,000us-gaap_Land
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
6,192,512,000us-gaap_Land
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
  6,295,404,000us-gaap_Land
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
Depreciable property Abstract        
Development in Process 1,343,919,000us-gaap_DevelopmentInProcess
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
988,867,000us-gaap_DevelopmentInProcess
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
  1,343,919,000us-gaap_DevelopmentInProcess
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
Land Available for Development 184,556,000us-gaap_LandAvailableForDevelopment
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
393,522,000us-gaap_LandAvailableForDevelopment
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
  184,556,000us-gaap_LandAvailableForDevelopment
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
Investment in real estate 27,675,383,000us-gaap_RealEstateInvestmentPropertyAtCost
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
26,800,948,000us-gaap_RealEstateInvestmentPropertyAtCost
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
  27,675,383,000us-gaap_RealEstateInvestmentPropertyAtCost
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
Accumulated depreciation 5,432,805,000us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
4,807,709,000us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
  5,432,805,000us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
Investment in real estate, net 22,242,578,000us-gaap_RealEstateInvestmentPropertyNet
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
21,993,239,000us-gaap_RealEstateInvestmentPropertyNet
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
  22,242,578,000us-gaap_RealEstateInvestmentPropertyNet
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
Cost of Property Repairs and Maintenance 473,098,000us-gaap_CostOfPropertyRepairsAndMaintenance
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
449,427,000us-gaap_CostOfPropertyRepairsAndMaintenance
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
332,219,000us-gaap_CostOfPropertyRepairsAndMaintenance
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
 
Acquisition of Archstone, net of cash acquired 0us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
/ dei_LegalEntityAxis
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4,000,875,000us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
/ dei_LegalEntityAxis
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0us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
/ dei_LegalEntityAxis
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Mortgage notes payable 5,086,515,000us-gaap_SecuredDebt
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
5,174,166,000us-gaap_SecuredDebt
/ dei_LegalEntityAxis
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  5,086,515,000us-gaap_SecuredDebt
/ dei_LegalEntityAxis
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Acquisition of Archstone Common Shares Issued 0eqr_AcquisitionOfArchstoneCommonSharesIssued
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1,929,868,000eqr_AcquisitionOfArchstoneCommonSharesIssued
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0eqr_AcquisitionOfArchstoneCommonSharesIssued
/ dei_LegalEntityAxis
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Payments of Financing Costs 10,982,000us-gaap_PaymentsOfFinancingCosts
/ dei_LegalEntityAxis
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16,526,000us-gaap_PaymentsOfFinancingCosts
/ dei_LegalEntityAxis
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21,209,000us-gaap_PaymentsOfFinancingCosts
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
 
Business Acquisition, Pro Forma Revenue   2,485,438,000us-gaap_BusinessAcquisitionsProFormaRevenue
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
2,317,699,000us-gaap_BusinessAcquisitionsProFormaRevenue
/ dei_LegalEntityAxis
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Business Acquisition, Proforma Income Loss From Continuing Operations   203,286,000eqr_BusinessAcquisitionProformaIncomeLossFromContinuingOperations
/ dei_LegalEntityAxis
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(54,940,000)eqr_BusinessAcquisitionProformaIncomeLossFromContinuingOperations
/ dei_LegalEntityAxis
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Business Acquisition, Proforma Income Loss From Discontinued Operations Net Of Tax   2,074,072,000eqr_BusinessAcquisitionProformaIncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
720,361,000eqr_BusinessAcquisitionProformaIncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
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Business Acquisition, Pro Forma Net Income (Loss)   2,277,358,000us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
665,421,000us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss
/ dei_LegalEntityAxis
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Business Acquisition, Proforma Net Income Available to Units   2,273,798,000eqr_BusinessAcquisitionProformaNetIncomeAvailableToUnits
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
651,548,000eqr_BusinessAcquisitionProformaNetIncomeAvailableToUnits
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
 
Business Acquisition, Pro Forma Earnings Per Share, Basic   $ 6.07us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
$ 1.74us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
 
Business Acquisition, Proforma Weighted Average Limited Partnership And General Partnership Units Outstanding Basic   373,421,000eqr_BusinessAcquisitionProformaWeightedAverageLimitedPartnershipAndGeneralPartnershipUnitsOutstandingBasic
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
370,837,000eqr_BusinessAcquisitionProformaWeightedAverageLimitedPartnershipAndGeneralPartnershipUnitsOutstandingBasic
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
 
Business Acquisition, Pro Forma Earnings Per Share, Diluted   $ 6.05us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_PartnershipInterestMember
$ 1.74us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted
/ dei_LegalEntityAxis
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Business Acquisition, Proforma Weighted Average Number Of Limited Partnership And General Partnership Unit Outstanding Diluted   375,861,000eqr_BusinessAcquisitionProformaWeightedAverageNumberOfLimitedPartnershipAndGeneralPartnershipUnitOutstandingDiluted
/ dei_LegalEntityAxis
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370,837,000eqr_BusinessAcquisitionProformaWeightedAverageNumberOfLimitedPartnershipAndGeneralPartnershipUnitOutstandingDiluted
/ dei_LegalEntityAxis
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Archstone Transaction [Member]        
Depreciable property Abstract        
Stock Issued During Period, Shares, New Issues   34,468,085us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementClassOfStockAxis
= eqr_ArchstoneTransactionMember
   
Acquisition of Archstone Common Shares Issued   1,929,868,000eqr_AcquisitionOfArchstoneCommonSharesIssued
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= eqr_ArchstoneTransactionMember
   
Average Price Per Common Share Issued   $ 55.99eqr_AveragePricePerCommonShareIssued
/ us-gaap_StatementClassOfStockAxis
= eqr_ArchstoneTransactionMember
   
Stock Issued During Period, Value, New Issues   1,200,000,000us-gaap_StockIssuedDuringPeriodValueNewIssues
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Public Offering [Member]        
Depreciable property Abstract        
Stock Issued During Period, Shares, New Issues     21,850,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementClassOfStockAxis
= eqr_PublicOfferingMember
 
Average Price Per Common Share Issued     $ 54.75eqr_AveragePricePerCommonShareIssued
/ us-gaap_StatementClassOfStockAxis
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Stock Issued During Period, Value, New Issues     1,200,000,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementClassOfStockAxis
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DelayedDrawTermLoan [Member]        
Depreciable property Abstract        
Term Loan Principal Amount   $ 750,000,000eqr_TermLoanPrincipalAmount
/ us-gaap_LongtermDebtTypeAxis
= eqr_DelayeddrawtermloanMember
   
Consolidated Rental Properties [Member]        
Depreciable property Abstract        
Properties acquired 6eqr_PropertiesAcquired
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= eqr_ConsolidatedRentalPropertiesMember
1eqr_PropertiesAcquired
/ us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis
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Property Units Acquired 1,353eqr_PropertyUnitsAcquired
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= eqr_ConsolidatedRentalPropertiesMember
322eqr_PropertyUnitsAcquired
/ us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis
= eqr_ConsolidatedRentalPropertiesMember
   
Land [Member]        
Depreciable property Abstract        
Land parcels acquired 2eqr_LandParcelsAcquired
/ us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis
= us-gaap_LandMember
1eqr_LandParcelsAcquired
/ us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis
= us-gaap_LandMember