Document and Entity Information (USD $) In Billions, except Share data	12 Months Ended
	Dec. 31, 2010	Jun. 30, 2009
Document and Entity Information [Abstract]
Entity Registrant Name	EQUITY RESIDENTIAL
Entity Central Index Key	0000906107
Document Type	8-K
Document Period End Date	May 23, 2011
Amendment Flag	false
Document Fiscal Year Focus	2010
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float		$ 5.9
Entity Common Stock, Shares Outstanding	0