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Investments in Partially Owned Entities - Summary of Company's Investment in Unconsolidated Entities (Parenthetical) (Details) | Sep. 30, 2021 Entity
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Projects Under Development [Member] |
Variable Interest Entity [Line Items] |
Number of unconsolidated interest in entities | 2
Real Estate Technology [Member] |
Variable Interest Entity [Line Items] |
Number of separate unconsolidated investment funds/Companies | 6

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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

X
- Definition Number of unconsolidated interest in entities. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- 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
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

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