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

Total number of units associated with properties acquired or completed and stabilized two or more fiscal years ago, less properties subsequently sold.

No definition available.

Name:	eqr_NumberOfUnitsInSameStoreProperties
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration