Business - Additional Information (Details)	Dec. 31, 2019 State Property ApartmentUnit
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Number of states in which entity operates \| State	10
Properties \| Property	309
Apartment units \| ApartmentUnit	79,962
ERPOP [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Noncontrolling interest, ownership percentage by parent	96.40%

Organization consolidation and presentation of financial statements disclosure.

No definition available.

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

No definition available.

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The number of real estate properties owned as of the balance sheet date.

No definition available.

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The number of states the entity operates in as of the balance sheet date.

No definition available.

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The number of units in a real estate property owned as of the balance sheet date.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
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Period Type:	instant

Name:	srt_OwnershipAxis=eqr_ERPOPMember
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