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Business - Ownership Breakdown (Details) | Sep. 30, 2018 Property ApartmentUnit
--- | ---
Property/Unit schedule |
Properties | Property | 306
Apartment Units | ApartmentUnit | 79,260
Wholly Owned Properties |
Property/Unit schedule |
Properties | Property | 286
Apartment Units | ApartmentUnit | 74,618
Master-Leased Properties - Consolidated |
Property/Unit schedule |
Properties | Property | 1
Apartment Units | ApartmentUnit | 162
Partially Owned Properties - Consolidated |
Property/Unit schedule |
Properties | Property | 17
Apartment Units | ApartmentUnit | 3,535
Partially Owned Properties - Unconsolidated |
Property/Unit schedule |
Properties | Property | 2
Apartment Units | ApartmentUnit | 945

X
- Definition The number of real estate properties owned as of the balance sheet date. + References No definition available. + Details
Name: | us-gaap_NumberOfRealEstateProperties
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition The number of units in a real estate property owned as of the balance sheet date. + References No definition available. + Details
Name: | us-gaap_NumberOfUnitsInRealEstateProperty
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_RealEstatePropertiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_RealEstatePropertiesAxis=us-gaap_WhollyOwnedPropertiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RealEstatePropertiesAxis=eqr_MasterLeasedPropertiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RealEstatePropertiesAxis=us-gaap_ConsolidatedPropertiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RealEstatePropertiesAxis=us-gaap_UnconsolidatedPropertiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |