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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
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Disclosure Of Entitys Reportable Segments [Abstract]
Units in same store properties	77,060	77,060

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