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

Number of major customers who contributed 10% or more to revenue during the period.

No definition available.

Name:	eqr_NumberOfMajorCustomers
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant