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

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- Definition Historical volatility estimation period. + References No definition available. + Details
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Namespace Prefix: | eqr_
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Balance Type: | na
Period Type: | duration

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- Definition 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. + References No definition available. + Details
Name: | eqr_HistoricalVolatilityPeriodBasis
Namespace Prefix: | eqr_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Summary of significant accounting policies. + References No definition available. + Details
Name: | eqr_SummaryOfSignificantAccountingPoliciesAbstract
Namespace Prefix: | eqr_
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Balance Type: | na
Period Type: | duration