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Reportable Segments - NOI for Each Segment from Our Rental Real Estate Specific to Continuing Operations (Parenthetical) (Details) - Property | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Segment Reporting Disclosure Of Entitys Reportable Segments [Abstract] |  |  |  |
Units in same store properties | 75,509 | 75,509 | 75,288 | 75,288

X
- Definition Total number of units associated with properties acquired or completed and stabilized two or more fiscal years ago, less properties subsequently sold. + References No definition available. + Details
Name: | eqr_NumberOfUnitsInSameStoreProperties
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration