Business (Details)	Dec. 31, 2016
Business (Textuals) [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent	96.20%
Number of States in which Entity Operates	10
Number of operating properties under long-term ground leases	13
Property/Unit schedule
Properties	302
Apartment Units	77,458
Wholly Owned Properties
Property/Unit schedule
Properties	280
Apartment Units	72,445
Master-Leased Properties – Consolidated
Property/Unit schedule
Properties	3
Apartment Units	853
Partially Owned Properties – Consolidated
Property/Unit schedule
Properties	17
Apartment Units	3,215
Partially Owned Properties – Unconsolidated
Property/Unit schedule
Properties	2
Apartment Units	945

Business.

No definition available.

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Number of operating properties for which the Company owns the building and improvements and leases the underlying land under long-term ground leases.

No definition available.

Name:	eqr_NumberOfOperatingPropertiesUnderLongTermGroundLeases
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Schedule of properties and units.

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.

Name:	us-gaap_NumberOfRealEstateProperties
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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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Period Type:	instant

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