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Reportable Segments - Additional Information (Details) - Customer | Sep. 30, 2017 | Sep. 30, 2016
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Segment Reporting Disclosure Of Entitys Reportable Segments [Abstract] |  |
Number of customer contributed 10% or more of total revenue | 0 | 0

X
- Definition Number of major customers who contributed 10% or more to revenue during the period. + References No definition available. + Details
Name: | eqr_NumberOfMajorCustomers
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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