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Commitments and Contingencies - Additional Information (Details) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2020 USD ($) Property ApartmentUnit Agreement
Projects in various stages of development | 2
Partially owned projects in various stages of development | 1
Units in various stages of development | ApartmentUnit | 824
Consolidated project under development commitment fund | $ | $ 377.1
Various stages of development with estimated completion dates ranging through September 30, 2021 | Sep. 30, 2021
Projects completed but not yet stabilized | 2
Number of joint venture agreements | Agreement | 2
Minimum [Member] |
Completed project current occupancy percent | 90.00%

X
- Definition Represents the company's remaining funding obligation (i.e. total project costs less book value) for consolidated projects that are under development. + References No definition available. + Details
Name: | eqr_ConsolidatedProjectUnderDevelopmentCommitmentFund
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Current occupancy percentage of completed project. + References No definition available. + Details
Name: | eqr_CurrentOccupancyPercentageOfCompletedProject
Namespace Prefix: | eqr_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of joint venture agreements. + References No definition available. + Details
Name: | eqr_NumberOfJointVentureAgreements
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of partially owned projects in various stages of development. + References No definition available. + Details
Name: | eqr_NumberOfPartiallyOwnedProjectsInVariousStagesOfDevelopment
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of projects completed but not yet stabilized. + References No definition available. + Details
Name: | eqr_NumberOfProjectsCompletedButNotYetStabilized
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total number of open development projects. May include projects that are held for and/or under development, completed and not stabilized or completed and stabilized. These projects are consolidated. + References No definition available. + Details
Name: | eqr_NumberOfProjectsInVariousStagesOfDevelopment
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total number of units that are associated with open development projects. May include projects that are held for and/or under development, completed and not stabilized or completed and stabilized. These units are consolidated. + References No definition available. + Details
Name: | eqr_NumberOfUnitsInVariousStagesOfDevelopment
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the latest completion date for the current projects under development. + References No definition available. + Details
Name: | eqr_VariousStagesOfDevelopmentDateMaturity
Namespace Prefix: | eqr_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |