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v3.21.2

Subsequent Events - Additional Information (Details) $ in Millions |  | 9 Months Ended
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Oct. 01, 2021 USD ($) Land | Sep. 30, 2021 Property
Subsequent Event [Line Items] |  |
Number of unconsolidated land parcel acquired | Property |  | 2
Land Parcels | Subsequent Event |  |
Subsequent Event [Line Items] |  |
Payments to acquire unconsolidated land parcel | $ 1.1 |
Land Parcels | Subsequent Event | Long-term Ground Lease [Member] |  |
Subsequent Event [Line Items] |  |
Payments to acquire unconsolidated land parcel | 5.8 |
Land Parcels | Subsequent Event | Commitment Agreement [Member] |  |
Subsequent Event [Line Items] |  |
Payments to acquire unconsolidated land parcel | $ 11.6 |
Number of unconsolidated land parcel acquired | Land | 2 |

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- Definition Number of unconsolidated land parcel acquired. + References No definition available. + Details
Name: | eqr_NumberOfUnconsolidatedLandParcelAcquired
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition The cash outflow associated with the investment in or advances to an entity in which the reporting entity shares control of the entity with another party or group. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=eqr_LandParcelsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_TypeOfArrangementAxis=eqr_LongTermGroundLeaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_TypeOfArrangementAxis=eqr_CommitmentAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |