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Investments in Partially Owned Entities - Summary of Companys Investment in Unconsolidated Entities (Parenthetical) (Details) - Entity | Dec. 31, 2020 | Dec. 31, 2019
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Real Estate Technology [Member] |  |
Variable Interest Entity [Line Items] |  |
Number of separate unconsolidated investment funds/Companies | 5 | 5

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- Definition Number of separate unconsolidated investment funds or companies. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_VariableInterestEntityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=eqr_RealEstateTechnologyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |