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Summary of Significant Accounting Policies (Details) (USD $)
Mar. 31, 2015
Dec. 31, 2014
Number of Real Estate Properties 389us-gaap_NumberOfRealEstateProperties  
Number of Units in Real Estate Property 108,793us-gaap_NumberOfUnitsInRealEstateProperty  
Noncontrolling Interests - Partially Owned Properties $ 122,661,000eqr_NoncontrollingInterestsPartiallyOwnedProperties $ 124,909,000eqr_NoncontrollingInterestsPartiallyOwnedProperties
Partially Owned Properties [Member]    
Number of Real Estate Properties 19us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= us-gaap_PartiallyOwnedPropertiesMember		  
Number of Units in Real Estate Property 3,771us-gaap_NumberOfUnitsInRealEstateProperty
/ us-gaap_RealEstatePropertiesAxis
= us-gaap_PartiallyOwnedPropertiesMember		  
Limited Life Partnership Properties [Member]    
Number of Real Estate Properties 6us-gaap_NumberOfRealEstateProperties
/ us-gaap_RealEstatePropertiesAxis
= eqr_LimitedLifePartnershipPropertiesMember		  
Noncontrolling Interests - Partially Owned Properties 10,992,000eqr_NoncontrollingInterestsPartiallyOwnedProperties
/ us-gaap_RealEstatePropertiesAxis
= eqr_LimitedLifePartnershipPropertiesMember		  
Noncontrolling Interests Settlement Value $ 63,300,000eqr_NoncontrollingInterestsSettlementValue
/ us-gaap_RealEstatePropertiesAxis
= eqr_LimitedLifePartnershipPropertiesMember