Summary of Significant Accounting Policies Compensation (Parenthetical) (Details)	12 Months Ended
Dec. 31, 2017
Summary Of Significant Accounting Policies [Abstract]
Historical period to estimate volatility	5 years
Historical volatility period basis	10 years

The historical time period (in years) used by the company to calculate the change in its stock price that is to be used in a fair value calculation.

No definition available.

Name:	eqr_HistoricalVolatilityPeriodBasis
Namespace Prefix:	eqr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration