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Equity, Capital and Other Interests EQR Common Shares (Details)
 3 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Common Shares of beneficial interest, shares outstanding 363,968,420us-gaap_CommonStockSharesOutstanding 362,855,454us-gaap_CommonStockSharesOutstanding
Common Shares Issued:    
Conversion of OP Units 154,050us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits  
Exercise of share options 770,012us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised  
Employee Share Purchase Plan (ESPP) 30,151us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans  
Restricted Share Grants, net 158,753us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures  
Units    
Common Shares And Units Outstanding 378,446,365eqr_CommonSharesAndUnitsOutstanding  
Units Ownership Interest in Operating Partnership 3.80%us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners  
Limited Partner [Member]    
Limited Partners' Capital Account, Units Outstanding 14,477,945us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
/ dei_LegalEntityAxis
= us-gaap_LimitedPartnerMember		 14,298,691us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
/ dei_LegalEntityAxis
= us-gaap_LimitedPartnerMember
Common Shares Issued:    
Conversion of OP Units (154,050)us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits
/ dei_LegalEntityAxis
= us-gaap_LimitedPartnerMember		  
Units    
Restricted units, net 333,304eqr_IssuanceOfLtips
/ dei_LegalEntityAxis
= us-gaap_LimitedPartnerMember