Commitments to Acquire/Dispose of Real Estate (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2010 Year Apartmentunit Hector Property LandParcels Project
Sales price-Rental Properties	$ 378,650
Properties Acquired-Total	2
Rental Units Acquired - Total	683
Properties Disposed - Total	15
Rental Units Disposed-Total	4,152
Commitments to Acquire Real Estate
Purchase Price - Total	$ 125,250

Commitments to Acquire of Real Estate Abstract.

Name:	eqr_CommitmentsToAcquireOfRealEstateAbstract
Namespace Prefix:	eqr
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Total number of rental properties to be acquired subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ Details

Name:	eqr_PropertiesContractedToBeAcquired
Namespace Prefix:	eqr
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Total number of rental properties to be disposed of subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ Details

Name:	eqr_PropertiesContractedToBeDisposed
Namespace Prefix:	eqr
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the fixed and determinable portion of an unrecorded purchase commitment for the acquisition of a rental property or land parcel subsequent to the balance sheet date.

+ Details

Name:	eqr_PurchasePriceForCommitmentsToAcquire
Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of the fixed and determinable portion of an unrecorded sales commitment for the disposition of a rental property or land parcel subsequent to the balance sheet date.

+ Details

Name:	eqr_SalesPriceForCommitmentsToDispose
Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Total number of rental units to be acquired subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ Details

Name:	eqr_UnitsContractedToBeAcquired
Namespace Prefix:	eqr
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Total number of rental units to be disposed of subsequent to the balance sheet date per separate agreements entered into prior to the balance sheet date.

+ Details

Name:	eqr_UnitsContractedToBeDisposed
Namespace Prefix:	eqr
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration