Real Estate Real Estate Acquisitions (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Acquired Properties	9
Units - acquired	1,896
Business Acquisition, Cost of Acquired Entity, Purchase Price	$ 968,545
Consolidated Rental Properties [Member]
Acquired Properties	9
Units - acquired	1,896
Business Acquisition, Cost of Acquired Entity, Purchase Price	906,305
Land Parcel [Member]
Acquired Properties	0
Land parcels acquired	5
Units - acquired	0
Business Acquisition, Cost of Acquired Entity, Purchase Price	$ 62,240

Total number of land parcel or parcels acquired from unaffiliated third parties during the period.

No definition available.

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- Definition

Total number of property or properties acquired from unaffiliated third parties during the period.

+ References

No definition available.

+ Details

Name:	eqr_PropertiesAcquired
Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Total number of units associated with the property or properties acquired from unaffiliated third parties during the period.

+ References

No definition available.

+ Details

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Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant