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Subsequent Events - Additional Information (Details) $ in Millions |  | 12 Months Ended
--- | --- | ---
Jan. 01, 2022 USD ($) Property ApartmentUnit | Dec. 31, 2021 Property ApartmentUnit | Dec. 31, 2020 Property ApartmentUnit
Subsequent Event [Line Items] |  |  |
Properties acquired | Property |  | 17 | 1
Property Units acquired | ApartmentUnit |  | 4,747 | 158
Subsequent Events [Member] |  |  |
Subsequent Event [Line Items] |  |  |
Properties acquired | Property | 1 |  |
Property Units acquired | ApartmentUnit | 172 |  |
Purchase Price | $ | $ 113.0 |  |

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- Definition Total number of property or properties acquired from unaffiliated third parties during the period. + References No definition available. + Details
Name: | eqr_PropertiesAcquired
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Total number of units associated with the property or properties acquired from unaffiliated third parties during the period. + References No definition available. + Details
Name: | eqr_PropertyUnitsAcquired
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of assets acquired at the acquisition date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123413009&loc=d3e4845-128472 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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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_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |