Derivative and Other Fair Value Instruments (Details Textuals 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2010	Dec. 31, 2009
Mortgage Loans on Real Estate [Line Items]
Mortgage loan issued	$ 650,000
Mortgage Loan Due In 11 Years [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage loan issued	$ 500,000
Maturity period of mortgage loan	11 years
Payment deferred as increase to interest expense, period		10

Represents the period of the loan during which the interest rate is fixed.

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

- Definition

Date when the debt is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

+ Details

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

- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 21
-Paragraph 16, 20

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration