Distribution Reinvestment and Share Purchase Plan (Details)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2008
Common Shares registered with Distribution Reinvestment and Share Purchase Plan (the "DRIP Plan")	4,850,000	5,000,000
Number of shares available for issuance	4,849,796
Discount range at which common shares can be purchased on a monthly basis with optional cash	0.00%
ShareBasedCompensationArrangementByShareBasedPaymentMaximumDiscountFromMarketPrice	5.00%

Represents the maximum discount from the market price which common shares may be purchased with optional cash payments made by participants in the dividend reinvestment plan or new investors.

No definition available.

Name:	eqr_Sharebasedcompensationarrangementbysharebasedpaymentmaximumdiscountfrommarketprice
Namespace Prefix:	eqr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration