Reportable Segments - NOI for Each Segment from Our Rental Real Estate Specific to Continuing Operations (Parenthetical) (Details) - Property	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Disclosure Of Entitys Reportable Segments [Abstract]
Units in same store properties	73,585	73,585	71,830

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