Business (Details)	Dec. 31, 2014
Property/Unit schedule
Wholly Owned Properties	364eqr_WhollyOwnedProperties
Master Leased Properties Acquired	3eqr_MasterLeasedPropertiesAcquired
Partially Owned Consolidated Properties	19
Partially Owned Unconsolidated Properties	3
Military Housing Properties	2eqr_MilitaryHousingProperties
Wholly Owned Units	98,287eqr_WhollyOwnedUnits
Master Leased Units	853eqr_MasterLeasedUnits
Partially Owned Consolidated Units	3,771eqr_PartiallyOwnedConsolidatedUnits
Partially Owned Unconsolidated Units	1,281eqr_PartiallyOwnedUnconsolidatedUnits
Military Housing Units	5,033eqr_MilitaryHousingUnits
Business (Textuals) [Abstract]
Number of operating properties under long-term ground leases	13
Number of land parcels under long-term ground leases	1
Noncontrolling Interest, Ownership Percentage by Parent	96.20%
Number of Real Estate Properties	391us-gaap_NumberOfRealEstateProperties
Number of Units in Real Estate Property	109,225
Number of States in which Entity Operates	12

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Total number of property or properties acquired from unaffiliated third parties during the period that are subject to a master lease arrangement under which the Company leases the property to a third party operator in exchange for net rental income.

+ References

No definition available.

+ Details

Name:	eqr_MasterLeasedPropertiesAcquired
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of units associated with rental properties that are subject to a master lease.

+ References

No definition available.

+ Details

Name:	eqr_MasterLeasedUnits
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of rental properties that represent military housing and are not consolidated by the Company.

+ References

No definition available.

+ Details

Name:	eqr_MilitaryHousingProperties
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of units associated with rental properties that represent military housing and are not consolidated by the Company.

+ References

No definition available.

+ Details

Name:	eqr_MilitaryHousingUnits
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	eqr_NumberOfLandParcelsUnderLongTermGroundLeases
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	eqr_NumberOfOperatingPropertiesUnderLongTermGroundLeases
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of rental properties that are partially owned and consolidated by the Company.

+ References

No definition available.

+ Details

Name:	eqr_PartiallyOwnedConsolidatedProperties
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of units associated with rental properties that are partially owned and consolidated by the Company.

+ References

No definition available.

+ Details

Name:	eqr_PartiallyOwnedConsolidatedUnits
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of rental properties that are partially owned and not consolidated by the Company.

+ References

No definition available.

+ Details

Name:	eqr_PartiallyOwnedUnconsolidatedProperties
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of units associated with rental properties that are partially owned and not consolidated by the Company.

+ References

No definition available.

+ Details

Name:	eqr_PartiallyOwnedUnconsolidatedUnits
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

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Balance Type:	na
Period Type:	duration

- Definition

Total number of rental properties that are wholly owned and consolidated by the Company.

+ References

No definition available.

+ Details

Name:	eqr_WhollyOwnedProperties
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of units associated with rental properties that are wholly owned and consolidated by the Company.

+ References

No definition available.

+ Details

Name:	eqr_WhollyOwnedUnits
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- 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